LAB FINAL!! IR, TLC, Simple Distillation, Gas Chromatography, Dehydration of cyclohexanol, WHMC, Natural Products and Alkenes, Kinetics, Oxidation, Phase Transfer Catalysis

positive ferric chloride

red, blue, purple, or green color

what does the solvent do

aid in the dissociation of the alkyl halide

how to detect alkene vs aldehydes, ketones (especially acetone), amines, and phenols

aldehydes, ketones, amines, and phenols add bromine by substation (not addition) and produce HBr

just above 3000 (3000 - 3100)

alkenes and aromatics

bromine test dectects

alkenes/alkynes

dehydration is often used to prepare _____ from ____

alkenes; alcohols

effect of diluting a reactant before mixing

allows heat to dissipate

doublet above 3000

amines

what is the greatest limit of tlc

amount of sample size that can be used is very small

what is IR not great at doing

analyzing complex samples

How do the bromines add in this rxn

anti

the lower layer in this lab will be the

aqueous layer

How does the FTIR handle air interference

at the beginning of the day the IR takes a background reading which it subtracts (imagine zeroing out a scale)

fractional distillation can be used on compounds with ______ bps but requires a ______ sample

closer;larger

what do organic reactions usually have

competing pathways; yield more than one product

requirements for steam distillation

compound can't be water soluble must be thermally stable

sublimation

compound goes from solid to gas skipping liquid phase

requirements for using gc or distillation

compound must be volatile compound must be thermally stable

volatile compound

compound that can be converted to gas phase at a reasonable temp without decomposition

polymorphic compound

compound with more than one pure crystalline form; each form has different mp

what does it mean when it says that a gas chromatography sample must be dry

contain no water

flow controller

controls the rate of flow of helium

ferric chloride dangers

corrosive, staining, not toxic though

crystal dissolves in solvent at room temp

crap

crystal doesn't dissolve in hot solvent

crap

in this lab cyclohexanol will be dehydrated into

cyclohexene

positive bromine test

dark orange -----> clear

what will the spot look like if you have plenty of sample

dark purple

because the coatings are made of organic materials they will _____ at high temps. For this each column as a maximum _____ _____

decompose; operating temp

what is a risk of distilling a super high boiling compound

decomposition

solubility of a dissolved gas _____ with temperature

decreases

when cleaning what should be done

dehydrating acid container should not be cleaned with acetone bc they react violently with each other

purpose of gas chromatography in the simple distillation lab

determine the percentage of component in each fraction

best ATR crystal

diamond

a mixture melting point of two different compounds will have a melting point that is _____ than either of the two pure compounds

different

why do spots differ in how far they go

differential adsorption and dissolution in the solvent

rf equation

distance spot moved/distance solvent traveled

theoretical plate

each condensation and vaporization step

what if not all of the compound melts

salt (inorganic/organic) or impurity

weaknesses of Baeyers test

gives false positive with easily oxidizable functional groups like aldehydes, ketones, and 1'/2' alcohols

joint freezing

glass expanding locking glass pieces together

advantage of tlc

great separation and excellent sensitivity

neutral bromothyol

green

more theoretical plates = more _____

separation

tlc is a _______ technique

separation

distillation

separation based on difference in boiling points of constituents in a mixture of miscible materials

breathing in bromine/getting it on skin

serious chemical burns

what should and shouldn't a good solvent do

should dissolve the reactant; shouldn't undergo competing rxn

why should acid be added slowly

heat is evolved

source of most natural products

plants

advantage of dual beam IR

prevents detection of functional groups in the air

Recyrstallization

process of dissolving solid material into a solvent and allowing it to recrystallize

why will the chromium reagents not be used in this lab? What will be used?

produce toxic non volatile salts; bleach

bleach + acid

produces hypochlorous acid (the actual oxidizing agent)

what effect does thicker plates have on chromatography

provide excellent separation, but don't have as good sensitivity

what do spectroscopic techniques such as FTR and NMR do

provide many data points for comparison with known materials

reverse phase tlc

silica gel has been derivatized and aliphatic hydrocarbons have been chemically bonded to SiOH groups present on the surface of the adsorbent.

adsorbent usually used in tlc

silica or alumina

which type of distillation will be be using in this lab

simple

what two things does flow rate depend on

size of column conditions necessary for separation

why should the solution be added slowly during filtration

so you do not float the filter paper and allow impurities to get into the purified sample

what reagent will be used to test solubility

sodium bicarbonate

how will excess oxidant be destroyed

sodium bisulfate

bleach

sodium hypochlorite

why should the sample not contain water

- water tends to contain dissolved solids in it such as sals that will clog the injector -water will degrade the column; columns are expensive -water signals are broad on the GC and make it hard to interpret ate

simple distillation provides good separation for liquids with boiling points that are at least ______ degrees apart

25

temperature difference between distillate and condenser require to cause condensation

25 degrees

sn1 is how many steps? which one is slow?

2; first one

which dehydrates faster, a 3' or 1' alcohol

3'

wich carbocation is most stable

3'

sharp doublet at 2500

CO2 (not part of sample)

What might air generate in an FTIR spectrum

CO2 in air may cause doublet peak between 2000 and 2500

solvolysis

SN1 reaction in which the solvent is the nucleophile

retention time

The time for a component to pass through a chromatographic column up to the detector.

after identifying the first major peak, what should you look for?

a confirming peak

what happens during the Baeyer test

a cyclic manganate ester is formed and then hydrolyzed into cis-1,2-cyclohexanediol

How is IR done on solid samples

a device that creates force/pressure is applied to the sample to ensure close contact

what will happen if the temp difference between the condenser and the distillate is less than 25 degrees

a lot of the vapor will escape

what type of solution are most rxns carried out in?

homogenous

what would happen if the column were allowed to rest on the sides of the oven

hot spots might develop messing up separation

safety precautions mp capillaries

hot/break easily

factors that affect how strongly the coating interacts with vapor

how much coating was used character of support

what is a fourth factor to keep in mind when choosing the type of chromatography; when must you keep this in mind

how much sample an be used (capacity); when using chromatography to separate

what cause the carboxylic acid group to range so far

hydrogen bonding

which drug is a racemic mixture

ibuprofen (only S isomer has analgesic activity)

presumptive identification

idea that you can rule out all ridiculous things, but never 100% confirm close thing

parts of a buchner funnel vacuum filtration

flat filter paper buchner funnel filter adapter/filter vac (seals buchner to erlenmeyer/suppport) clamp hose to connect flask to aspirator filter flask

what field uses ATR/FTIR frequently

forensic science

what does the co2 produced by carbonic acid do

forms bubbles in the solution

how are functional groups detected

functional groups absorb IR energy at very specific wavelengths

in gc what is the fluid

gas

how to detect HBr

gently blowing across the top of the test tube. The moisture in your breath will condense with it and produce a fog if HBr is present

why are things like melting point, boiling point, smell, and density not always useful

give no structural information

why are plastic pipettes used instead of glass pipettes

glass pipettes may scratch the ATR crystal

crystal doesn't dissolve at room temp, but will dissolve when solvent heated

good; move onto cooling the solution to create recrystallization

how to increase sped of rxn if it is slow

heat it

how is distillation carried out

heating a liquid to boiling and then collecting the condensed vapors

gas usually used in gc

helium; although sometimes n2 or other gases used

when should the tube be removed

hen the signal for the peak returns near baseline (or near the start of the signal for another component),

compounds held together by ionic bonds tend to have ____ melting points

high

do samples with close booing points have high or low reflux ratios

high

what makes steam distillation special

high boiling materials that are present in tars, oils, plant matter, or other hard-to-manage materials are distilled at temperatures well below their true boiling points in the presence of steam (water vapor).

why does vapor pressure increase with temp

higher temp = more mlcs going into gas phase = higher vapor pressure

when will a mixture of alkenes result

if the carbocation can lose chemically different alpha hydrogens

what does fractional distillation do

improves separation (fractioning)

melting point range broader than two degrees

impure

resolution ____ with theoretical plates

increases

vapor pressure ____ with ______ temp

increases; increases

way to increase number of theoretical plates

increasing length of column

column packing is usually ____ and ____

inert; organic

what else may analgesics contain

ingredients not directly related to pain relief such as caffeine

which fractions have the highest purity

initial and final

more coating = more _______

interaction

what can amino acids do to ibuprofen? What is this process called

interconvert S and R configurations; glucuronidation

where does the ir beam go once it has traveled the length of the crystal

into the detector

why do impurities lower melting point

introduce entropy into the lattice, lowering the amount of nrn needed to break it

phase transfer catalysis is often used when one of the reactants is an _____ ______

ionic nucleophile

which test is superior?

potassium permanganate; reacts with aliens that are not reactive enough to decolorize br

how should you not pack a capillary tube? Why?

pounding it on the bench between your fingers, the tube could shatter and cut, if not go through, your fingers.

preparative chromatography differs from tlc in what way

preparative chromate uses thicker plates

what is one of the uses of gc

separate a mixture of components

what happens if the solution is not slowly cooled

small impure crystals form

how steam distillation lowers boiling point

their combined vapour pressures are bound to reach the external pressure before the vapour pressure of either of the individual components get there.

type of detector used in this gc lab

thermal conductivity detector

when do organic chemists usually choose to use recrystallization

thermally unstable compounds (decompose when you try to take melting point) high melting solids

why are injector points dangerous

they are hot

Do rxns in ocher go perfectly? What usually happens?

they don't go to completion or form a mixture of products

which functional groups are easiest to detect

those that contain oxygen

what type of materials is steam distillation useful for

those that may decompose at high temps

disadvantage of using more theoretical plates

time and money

most common form of chromatography

tlc and gc

Purpose of using tlc analgesic lab

to identify the major active ingredients in an unknown analgesic

why is the buchner funner heated in water

to prevent crystallization on the walls of the buchner funnel

why should you grease

to prevent joint freezing

what is the solvent used in this lab

water

what should not be used as a solvent in this lab

water

what solvents are usually used in reverse phase tlc

water and alcohol

what does carbonic acid rapidly decompose into

water and co2

best known azeotrope

water and ethanol

spill acid on skin

water followed by sodium bicarbonate

what products are usually distilled by steam distillation

water insoluble oils; h/e can be done on some solid organic materials

cyclohexene will be washed with ____ followed by _____

water, NaCl

spill potassium permanganate on skin

water,soap

____ is eliminated to form a _______ ______ ______bond

water; carbon-carbon pi

what is not required for the condensation of liquids with boiling points above 150? why

water; the difference between the boiling point of the liquid and the condenser is so great that it doesn't require water to condense

intensity of peaks in the 3000-3100

weak to medium

what should be done to the filter paper

wet it with hot solvent so it sticks to the funnel

when should dehydration not be used

when alcohol contains other functional groups

when is fractional distillate preferred

when bp difference between the liquids is less than 20 degrees

when should you record the temperature

when the first drop lands in the receiving flask

when do the best crystals form

when the solution is cooled slowly

isocratic

when the temp during gc remains constant

ramped up

when the temp is fluctuated during gc

more surface area = ____________ theoretical plates

more

what does elute mean

move up

regional most useful for comparing isomers with same functional group

1400-400

what boiling point can simple distillation can safely done up to

150 degrees

most commonly used ATR crystal

ZnSe

we want the compound to crystallize _____ impurities have been removed

after

large peak at 3200

alcohol or phenol

primary alcohol

aldehyde

2200 peak

alkyne or nitrile (both types of triple bonds)

why is the yield of cyclohexene usually high with cylohexanol

all the alpha hydrogens are chemically the same, meaning deprotonation results in only one type of alkene

what happens if the sample is a solid

dissolved in a solvent other than water

what does water do to normal tlc

dissolves adsorbent and hydrated calcium carbonate

____ most useful technique for separating and identifying compounds

chromatography

stereochemistry of Baeyer's test? Why?

cis; cyclic intermediate

signs of sublimation

crystals may form at top of capillary tube (do to gas condensing)

weird way to calculate peak composition

cut out and weigh them

heating mantles should never be

directly connected to an outlet

what does the water produced by carbonic acid do

dissolve the ionic salt formed by sodium bicarbonate

retention time formula

distance from start to center of peak (max height) / rate

how to lessen polymerization and substitution

distill cyclohexene as it is formed

why do tertiary alcohols not undergo oxidation

do not have a hydrogen on the a-c

how do you decide which purification method to use?

easiest procedure fastest procedure which will give best results

resolution

efficiency of separating components in the distillation mixture

what type of reaction is this

elimination

why is the heated block kept 10 degrees above the column

ensures that volatile compound will not condense in the detector

vapor pressure of immiscible liquids

equal to the sum of the vapor pressures of the individual parts

what does the ability of tlc to separate depend on

equilibrium between solvent, non mobile adsorbent, and the sample

what type of container should be used for recrystallization? Why

erlenmeyer flask, crystals can escape from beakers

which two compounds will not decompose at high temps

ester or aromatic

why is ethanol a good solvent for dehydrohalogentation of alkyl halides by potassium hydroxide

ethanol polar enough to dissolve ionic potassium hydroxide, and organic enough to dissolve alkyl halide

liquids with high vapor pressure will _____ quickly

evaporate

how are adsorbents dangerous

fine powder, may get into eyes and hurt and cause corneal abrasions

what reagin of the ir will be examined for this lab

fingerprint

what should you not use to put out a recrystallization fire, why?

fire extinguisher; too powerful/ creates a mess

what is the packing material made out of

firebrick (inert clay that can withstand high temps)

distillation

method for purifying volatile compounds

gas chromatography

method for quantitatively determining the relative proportions of compound in each sample

the two liquids in simple distillation must be

miscible

azeotrope

mixture of two or more liquids with a single sharp boiling point

the smaller the difference in boiling point, the _____ theoretical plates you need for separation

more

the thermal conductivity sector is the ______ common and the _____ sensitive

most; least

disadvantage of fractional distillation

much slower

most recent otc analgesic

naproxen

will pure compounds have a broad or narrow range

narrow (1-2 degrees)

can azeotropes be separated by distillation

no

will the solvent used to dissolve the sample have an affect on retention time

no

why is a thermocouple not used in stem distillation

no fractions are taken and the distilling temperature will vary little from the boiling point of water

the carbocation can react with nucelophiles to form substitution products, why did this not happen in this lab

no good nucleophile present in the dehydrating acid

tertiary alcohol

no rxn

will water damage the ATR

no, but it will show up in the spectrum so dry the sample

should you blow on the acetone to make it dry faster

no, metabolites in your breath will show up on the IR

is dehydration by a strong proton acid gentle

no, subjects alcohol to harsh conditions

in normal phase chromatograpy _____ compounds will move the farthest

nonpolar

which type of tlc was used in the analgesic experiment

normal phase

why can cotton not be used as a plug

not stable at high temps

what happens to the intermediate carbocation

not stable in the aqueous environment and is rapidly hydrated (water adds to the carbocation) to yield a protonated alcohol

advantages of FTIR

samples that were once too small can now be run

FTIR stands for

Fourier transform infrared

boil up rate

volume of liquid that enters the column as vapor per minute

when to use gc instead of distillation

- very little sample (main) -samples have identical bps but different functional groups -can be used on compounds not thermally stable enough to survive distillation

below 925

-aromatic hydrocarbon (one or more strong peaks) -aliphatic roll (caused by hydrocarbon chain rotating) -broad triangular absorption indicates carboxylic acid -halogenated hydrocarbon (can be caused by not removing all of dichloromethane)

three factors to keep in mind when choosing which type of chromatography to use

-best separation (resolution) -highest sensitivity -speed of separation

map signs that the compounds are different

-broad mp range -mp way different than pure mp

what are the four factors of the chromatography tetrahedron

-capacity -resolution/separation -purity/sensitivity -speed

two requirements for gc

-compound must be volatile -compound must be thermally stable

features of most organic reactions

-each reactant dissolved in a solvent -one solution is added slowly to another -extothermic

components of a good qualitative test

-fast -easy -gives easily detectable change (i.e. color or gas evolution) -specific for a particular functional group

three advantages of Spectroscopy

-fast -nondestructive -only small amount of material required

what are adsorbents mixed with, why?

-inorganic material such as gypsum or hydrated calcium carbonate (allows it to stick to plate) -inorganic fluorescent material

why should you not use too much grease

-it will get into sample -less grease = surface tension=slows down erosion of grease

signs of decomposition

-material darkens (obvious color change) -effervescing -evolution of liquid (droplets condense at top of capillary tube)

two purposes for determining mp

-measure of purity -identifying unknown

what are the 5 major types of chromatography

-paper -gas -flash -thin layer -column

advantages of FTIR over dispersive IR

-signal is much stronger -can do multiple scans and combine them to generate highly accurate IR -spectrum automatically calibrated with He-Ne laser

giant blob at the top of the plate means

-solvent is contaminated -plate was overloaded with too much sample which destroyed resolution (separation) -spot was too large (equilibrium not established)

what could yield a negative bromine test

-unreactive alkene -electron groups on c=c bond slowing rxn

what is one way to proven the solvent front from moving too far, problems with this?

-use you pencil to scratch a line; no adsorbent = no movement -tend to stop watching it and leave it in too long...solvent will spread out and mix dots

Rf values can range from

0 to 1

how big should spots be ideally

1-2 mm

what are the the two regions the 2000-1600 is dived up into

1. 2000-1667 2. 1650 -1600

what are the first three areas you should you focus on for IR

1. 3600-3000 2.1800-1600 3.1200-1000

which set of crystals produced by the mother liquid is most pure

1st set

spill bromine on skin

warm water, soap, followed by sodium thiosulfate

procedure for experimentally finding a good solvent

1. attempt to dissolve some crystal into the solvent; if it dissolves at room temp, the solvent is crap 2. if crystal doesn't dissolve, attempt to heat the solvent 3. if the crystal still doesn't dissolve in the hot solvent, then the solvent is crap 4. if the solvent does dissolve, when the solvent is hot allow the solution to cool and recrystallize 5. if crystal form it is great!!!

recrystallization procedure

1. dissolve impure compound in hot solvent 2. continue adding solvent until no more compound dissolves (i.e. only impurities remaining) (always add less solvent than you did previously) 3. remove any impurities using a hot vacuum filtration 4. after removing impurities allow the solution to cool 5. once the solution has cooled to room temp you can place it in ice water bath 6. once solution is ice cold , vacuum filter it again 7. dry/weigh sample and obtain melting point

what are the two major goals of successful recrystallization

1. get the maximum amount of purified compound back as a solid 2. purify the sample

what are the second three areas you should focus on for IR

1. just above 3000 2. 2000-1600 3. below 925

tips for picking a good solvent

1. solvent should not chemically react with compound 2.solvent should dissolve compound while hot 3.the same solvent should not dissolve the compound while cold 4.solvent should dissolve the impurities at all temps or not at all

three factors resolution depends on

1.theoertical plates 2. boiling up rate 3.reflux ration

where is the fingerprint region

1500-400

anything above _____ intensity is too strong to be an aromatic substitution

30%

how many major techniques are there to purify/separate samples

4

what is the FTIR range

4,000 to 4000

where are the majority of functional groups found

4000-1500

mid peak absorbance

50%

Which part of the FTIR range doesn't provide much structural information

600 to 400

what temp must the experiment be kept under to avoid distilling cyclohexanol as an azeotrope

90

Asprin

ASA (acetylsalicylic acid)

Naproxen Sodium

Aleve and Naprosyen

oxidizing agents usually contain

Cr

How does ATR work

IR beam passed through beveled crystal(internal reflectance element) at 35-45 degree angle (45 for liquids).....causes beam to reflect down crystal.....as the beam reflects down the crystal it penetrates about one micrometer into the sample

fase negative bromine test

If an electron withdrawing group is neighboring the double bond or if you have unusual steric hindrance

what should you not do before Bromine test

wash test tube with acetone

the IR used to not be very popular, what changed?

It's identification abilities are unmatched;amazing at identifying and detecting functional groups

cause of ferric chloride color complex

Most phenols form colored complexes upon reaction with ferric ion, Fe3+

why is proton acid catalysis required

OH is a poor leaving group

how does recyrystalliation purify a compound

Recrystallization takes advantage of the fact that most crystal growth prefers incorporation of molecules of the same structure - leaving other structures (impurities) out of the crystals.

false positive ferric chloride

Some carbonyl compounds with a high equilibrium concentration of enol can give a false positive response to this test.

advantage of steam distillation

able to vaporize and distill a material at a temperature well below its boiling point.

how far does the ir penetrate into the sample

about 1 micrometer

where should your origin and spots be relative to the solvent

above

strong peak absorbance

above 70%

three most common orc pain killers

acetaminophen aspirin ibuprofen

what compound will be dissolve in this lab

acetanilize

____is used to clean the ATR

acetone

why should you allow acetone to completely dry before loading your sample

acetone will show up in the IR

which type of dehydration will be used in this lab

acid catalyzed

what technique can be used if the solution is dark in color(i.e) not the right color

activated carbon

what should you do if an oil forms

add more hot water

what is the difference between fractional distillation and simple distillation

addition of a fractioning column

why might these non-analgesics be added?

advertising purposes

ibuprofen

advil/motrin

should you turn of the water before or after disconnecting the tubing

after

mechanism of permanganate test

attack of two oxygen atoms of the permanganate ion, MnO4- on the pi bond of an alkene or alkyne resulting in a change in oxidation state of the manganese ion, resulting in the disappearance of the very deep purple color of permanganate and the simultaneous formation of a brown precipitate of manganese dioxide (MnO2)

ATR stands for

attenuated total reflectance

in azeotropes, the vapor and the liquid have the composition of the ______

azeotrope

minimum boiling azeotrope

azeotrope that boils at temp below the boiling point of the liquids in the mixture

is sodium bicarbonate a weak acid or base

base

how will eugenol be obtained

base extraction

where is the thermocouple placed in micro-distillation

base of the distillation head

how does non polar coating separate

based on differences in boiling point rather than polarity

how are the vapor components separated

based on their interaction with the packing material coating

why is it better to decant the cyclohexene away from the calcium chloride rather than filter it out

because cyclohexene is volatile

slower boil up rate = ____ resolution

better

larger reflux ratios = _____ resolution

better (more liquid coming back than being distilled)

DMF danger

birth defects

how to put out a fire

blow it out, or smother it using damp towel, watch glass, beaker, etc

basic bromothyol

blue

what color will the test turn

blue black

how is hcl colorized

bromothyol blue

potassium permanganate on skin

burns and stains

DMSO danger

burns through skin

how is the rxn monitored

by following the rate of acid formation

peak from 1200 to 1000

c-o group

1650 to 1600

c=c (indicated by medium intensity sharp peaks)

what is now possible with the use of a catalyst

can transfer reactant between aqueous and organic phase

what principle allows the solvent to move up the plate

capillary action

when will polymerization occur

carbocation adds to the alkene

what happens in the last step

carbocation rapidly loses proton from the adjacent alpha carbon forming double bond

peak from 1800-1640

carbonyl group

alcohols are oxidized to form

carbonyls

inverted mountain peak from 3200-2500

carboxylic acid

the _____ _____ is essential to gc

carrier gas

septum purge

carrier gas flowing just below septum prevents vapor from sticking to septum and contaminating future gas

why are chemwipes not used to clean the ATR

chemwipes have an abrasive in them that may scratch the ATR crystal

how can cyclohexene be removed

it forms an azeotropic mixture with water which is distilled out

how does gc differ from other separation methods in terms of theoretical plates

it has tons (2500)

why can't an unknown liquid with a constant boiling point be called pure

it may be an azeotrope

what happens when the upward flow of the solvent reaches equilibrium

it will stop moving up and the solvent will begin to spread out (i.e. mixing spots together)

where should the thermocouple be placed

just below the lip of the condensation assembly

secondary alcohol

ketone

why is phenacetin no longer used

kidney damage/possible carcinogen

acetone + bromine

lachymator

simple distillation requires the ____ amount of theoretical plates compared to other methods

least

what does the number in reverse tlc represent

length of aliphatic chains

higher the rate of temp, the _____ theoretical plates

less

less theoretical plates = ____ separation

less

weak beak absorbance

less than 30%

rule for insolubility in water

less than one OH per 5-6 carbons

why can some compounds be purified by gc and not by distillation

less time at higher temp

why does melting point depression occur

liquid formed from melting must dissolve some of the other material

mother liquor

liquid in the filter flask containing soluble impurities and pure sample

why does gas chromatography not always work on organic compounds

not sufficiently volatile at temperatures below their decomposition temperatures

why is below 925 significant

nothing really shows up here

larger reflux ratios = ____ distillation time

longer

relationship between aliphatic chain and organic compound affinity

longer chain = more affinity

length of column

longer column = longer retention time

Why are qualitative test not the bests

lose material, ambiguous, can't 100% identify, etc....

what does the rate of reaction depend on in this lab

loss of the leaving group to form a carbocation

which step is slow in E1

loss of the leaving group to form a carbocation

liquids with high vapor pressure will have ____ boiling points

low

sample spends more time in gas phase than in liquid phase

low retention time

do mixtures of different compounds usually have higher or lower mp?

lower (melting point range starting below the melting point range of the lowest melting point of the two organic materials.)

high temp

lower retention time

fast flow rate of carrier gas

lowers retention time

2000-1667; when do we care about these

lumps and bumps corresponding to aromatic substitutions (only if they are weak and broad)

what are the two types of apparatuses used in simple distillation

macro and micro scale

purpose of starch test

make sure there is enough bleach

why is reverse phase tlc called reverse phase

many of the solvents and properties are reversed

solvent doesn't rise above origin

marked too hard with pencil removing adsorbent

nonvolatile material

material with a very low vapor pressure

why does a sharp melting point not guarantee a pure compound

may be a eutectic mixture

how to determine rate of chemical rxn

measure the concentration of either reactants or products as they change over time

melting point can be more accurately described as a

melting range

although recyrstallization is usually performed using a solid sample, recyrystallization is occasionally performed on ______ a _____

oil; liquid

when is vacuum filtration used in this lab

once to remove insoluable impurities form the hot filtrate once isolate purified crystals from remaining isolate

what is the main difference in the two types of filtration

one is cold and one is hot

easiest type of product to purify

one that is relatively pure already

should the apparatus be open or closed?

open, a closed system will explode

point of the tetrahedron

optimizing one point means sacrificing one of the other three

what part of recrystallization is very flammable

organic vapors

how should you measure spot distance

origin to middle of spot

spot looks like one big trail

overloaded plate or solvent not sufficiently polar

what happens in oxidation

oxidizing agent removes two hydrogens (one from the a-c) and one from the alcohol

____ used to be used in lieu of _____ (pain killers)

phenacetin; aspirin

ferric chloride test

phenols

compounds that can cause a false positive bromine test

phenols, enols, amines, aldehydes, ketones (substitution rather than addition)

melting point physics definition

physical measure of the forces holding molecules of a compound into a crystal lattice

natural products isolated from plants

phytochemicals

slick trick for saving tlc plate

place tape over it

over-spotting or co-spotting

placing one spot on top of another in order to confirm that it is the same compound

in reverse phase chormatography _____ compounds will move the farthest

polar

what type of solvent is used

polar

method for solving solubility issues in past

polar aprotic solvents such as DMSO and DMF can dissolve polar salts as well as organic materials

effect of polarity on retention time

polar coating + polar sample = longer retention time nonpolar coating = retention time based on bp

deciding factor in reaction pathway

polarity of solvent

what does an extreme rf value indicate

poor choice of solvent

three general steps of acid-catalyzed dehydration

protonation dehydration deprotonation

what does a fractioning column do

provides more surface area for the vapor to contact increasing the number of theoretical plates

why is it important to replace the septum

puncture holes in it will allow carrier gas and vaporized sample to escape

What does recrystallization do?

purify impure samples

number one major concern of organic chemists

purity of product

positive Baeyer's test

purple ----> dark brown manganese dioxide precipitate

was qualitative or quantitative data collected in analgesic TLC lab?

qualitative (want to see what is present, not how much)

besides being good for isolation/purification, what else can tlc do

quantitative tool for telling you how much of each component present

purpose of vacuum filtration

rapidly separating solids from liquids

why are rf values useful

rate at which organic compound elutes is highly characteristic and can be used to id it

what does Rf stand for

ratio of fronts retention factor

solubility issues in rxns

reactants tend to have diff solubilities

sodium bicarbonate mechanism

reacts with ptotic acid to form sodium salt and carbonic acid

flourescant finger print

really just a spot that wandered off

which experiment is most likely to cause a fire

recrystallization

what are the four major methods of purification

recrystallization extraction distillation chromatography

after hot filtration, what should be done if crystals form

reheat and stir

purpose of drying tube

removes moisture from gas extending the life of the column and detector

what to do if product is still remaining in funnel

rinse sample flask with hot solvent and pour that into funnel, then wash the funnel/filter paper with more hot solvent

calculating percent composition

same as area of triangle A=height of peak * width at half height

what is something that makes recrystalliztion unique compared to the other four major purification techniques

sample most be solid

What is the issue with sample preparation

sample must be in the path of the beam, means it can't absorb nrg between 40000-400 ( all organic/most inorganic do) (esp ones containing oxygen)

in order to perform recrystallization, the material to be purified most be __________

solid

If the compound you are purifying is known, what type of information can you get from the handbook

solvent mp bp color of purified compound (assume white or colorless if unspecified) crystalline form (ex. flakes, needles, etc)

compound doesn't reappear after cooling

solvent crappy

what will a liquid at any temp have?

some molecules escaping into the gas phase

how does tlc work

spots are placed on plate (glass, plastic, or aluminum) containing adsorbent....plate is placed in solvent......solvent travels up plate....as solvent passes spot, the spot partially dissolves into it

one big blob forms in middle

spots spotted too close together

what does the rate of an E1 rxn depend on

stability of carbocation

How is I2 colorized

starch

potassium iodide

startch test

how will limonene be obtained

steam distillation of orange peel

false negative ferric chloride

sterically hindered phenols do not give a colored complex

reflux ratio

volume of liquid returned to the distilling flask/volume of liquid removed as distillate

How do you get an IR spectrum for a seemingly empty vial

swab the vial and rub the swab on the ATR crystal

how/what did distillation used to be used for

taking dilute alcohol solutions and distilling them to give alcohol solutions with high concentrations

boiling point

temp at which vapor pressure = atmospheric pressure (bubbles able to form and rise bc the vapor pressure can overcome the atmospheric pressure)

melting point

temp range from when you see first crystal melting (or crumbling/collapsing) to when last one melts

peak at exactly 925

terminal =CH2

peak at 3300

terminal alkyne

what are the two natural products in this lab

terpene and acetogenins

what will happen if the column is subjected to a temp higher than the operating temp

the coating will vaporize and be carried out or decomposed effectively destroying the effectiveness of the column

the vapor condenses from simple distillation should contain more of what component

the component with a lower boiling point

what is done after performing the hot vacuum filtration

the filtrate is reheated to dissolve any crystals, the solution is then allowed to slowly cool

why are flow controllers important

the flow rates of the two streams must be balanced or the thermal conductivity detector will not work

what happens to gas when the gc use a thermal conductivity detector

the gas is split into two streams....one stream directed by injection port....other stream directed through another column to the detector

what will happen if a polar packing material like carbowax is used

the polar components of the sample will interact with it much more, taking a longer time to pass through the column resulting in a greater retention time

vapor pressure

the pressure exerted by a vapor over a liquid

ideally all of the sample will be flash vaporized, unfortunately this doesn't happen. What happens

the sample that is not flash vaporized remains as an aerosol that will travel with the carrier gas, not interacting with the column packing. This aerosol is detected as an air peak and will have the exact same composition as the sample

chromatography

the separation of a mixture into its components by passing the fluid over a non-mobile adsorbent and separating the components by differential absorption and elution

what will happen if you let tlc sit in solvent for too long

the solvent will run up and off the plate

Bromin Test forms what compound

trans-1,2-dibromocyclohexane

crystals don't form during recrystallization

try agitating the sample by shaking or rubbing the inside of tube with stirring rod; if all else fails try adding a little bit of impure sample

compound completely dissolves in solvent, solvent doesn't dissolve compound at all

try mixing these solvents

what is ATR penetration called

tunneling

what happens to iodide when it is oxidized

turns into I2 (little color)

how many times is vacuum filtration used in this lab

twice

how many hands should be used to handle a gc syringe

two

eutectic point

unique mixture of A and B that has a sharp melting point; also point where the mixture melts at the lowest temperature observed for any mixture of the two compounds

cause of azeotrope

unknown; no relationship

Baeyer test (potassium permanganate) tests for

unsaturation

how long will the azeotrope distill for

until one of the components is exhausted

often textbooks and google will give one number for the mp, what is this

upper limit of the range

calcium chloride

used to dry cyclohexene

why are two hands used to handle the gc syringe

using one hand my bend the wire

in gc the sample is

vapor

Raoults Law

vapor pressure always proportional to the mole fraction of each component

benefits of caffeine

vasodialator; cuts relief time in half

sport ran off the side of the plate

very wet sample or defective plate

advantage of tcd over other detectors

volatile components can be collected unchanged as they leave the detector. This allows a GC equipped with a TCD to be used for the purification of relatively small quantities of volatile material While this collection may be slow and tedious, it is one of the most rapid methods for the purification of small quantities (less than 1 mL) of volatile compounds.

simple distillation is used to separate a ____ liquid from another soluble ________ or ______ impurity

volatile; nonvolatile; less volatile

acidic bromothyol

yellow

can a combination of solvents be used to reach the ideal solvent?

yes

is it okay to use more than one technique in conjunction

yes!

what will happen if purification has taken place

your starting sample will weight less than your beginning sample