orgo quiz 2
water solubility
- Ionic - Organic ions of < 7-8 carbons - Small polar molecules - Organic compounds with one H-bond donor per 3-4 carbons
functional group region
4000-1450 in IR
b
A student carried out a simple distillation on a compound known to boil at 124 oC and they reported a boiling point of 116-117 o Analysis of the compound showed it was pure and calibration of the thermometer indicated that it was accurate. What procedural error might the student have made in setting up the distillation? a. Not insulating the distillation head with glass wool and aluminum foil b. The thermometer was placed too high in the distillation head c. Not adding anti-foaming agent d. Heating up the distillation too fast e. Not adding a boiling stone
impurities were left in the sample. the product could be contaminated or the student may have used tap water instead of distilled
A student recrystallized some impure benzoic acid and isolated it by filtration. He scraped the purified benzoic acid off the filter paper after it had dried and took the melting point as a test for purity. He was surprised that most of the white solid melted sharply between 121 and 122°C but that a small amount remained unmelted even at temperatures above 200°C. Explain this behavior.
his
Amino acids alanine (Ala), proline (Pro), cysteine (Cys) and histidine (His) are separated using TLC. Based on the Rf values provided, which amino acid has the highest affinity for the stationary phase? Ala = 0.34 Pro = 0.50 Cys = 0.82 His = 0.13
a
Based on the literature values of caffeine, why characterizing caffeine using melting point is not viable? (caffeine b.p. 170oC, m.p. 238oC) a. its vapor pressure as a solid exceeds the atmospheric temperature and sublimates b. Caffeine decomposes at its melting point c. We are recovering so little than running a melting point will be impossible
true
Because there is not an exact temperature to describe it melting point is more correctly called melting range (t/f)
c, e
Before extracting the caffeine with methylene chloride, you added Na2CO3 to the aqueous portion. What two things does the addition of base do to aid the extraction of caffeine? [check all that apply] 1. The base converts the tannins into their sodium salts, making them more soluble in water. 2. The base converts the tannins into their sodium salts, making them less soluble in water. 3. It deprotonates caffeine making them more soluble in water. 4. It deprotonates caffeine making them more soluble in dichloromethane. 5. It protonates caffeine making them more soluble in dichloromethane. 6. It protonates caffeine making them more soluble in water. a. It deprotonates caffeine making it more soluble in water. b. The base converts the tannins into their sodium salts, making them less soluble in water. c. The base converts the tannins into their sodium salts, making them more soluble in water. d. It protonates caffeine making it more soluble in dichloromethane. e. It deprotonates caffeine making it more soluble in dichloromethane. f. It protonates caffeine making it more soluble in water.
e and f
Before extracting the caffeine with methylene chloride, you added Na2CO3 to the aqueous portion. What two things does the addition of base do to aid the extraction of caffeine? [check all that apply] a. The base converts the tannins into their sodium salts, making them less soluble in water. b. It deprotonates caffeine making it more soluble in water. c. It protonates caffeine making it more soluble in water. d. It protonates caffeine making it more soluble in dichloromethane. e. It deprotonates caffeine making it more soluble in dichloromethane. f. The base converts the tannins into their sodium salts, making them more soluble in water
anti foaming agent
Chemical additive that reduces and hinders the formation of foam in liquids.
no. it is a salt and has a low ph
Could you use 1.0 M NaBr (sodium bromide) as your base in place of 1.0 M NaOH for your extractions? Why or why not? Briefly explain.
immiscible part of solvents, good solubility of target compound, poor solubility of impurities, volatility of extraction solvent, toxicity and safe properties of extraction solvent
Describe desirable properties of extraction solvents for liquid-liquid and liquid/solid extractions.
tlc carried out against gravity, cc run under gravity, tlc requires less time to separate, tlc needs more polar solvent
Difference between TLC and Column Chromatography
false
Every time the compound is contaminated the melting range will go up. (t/f)
caffeine is an organic compound and dcm is an organic solvent and like dissolves like
Explain why caffeine migrates to methylene chloride from aqueous phase during the liquid-liquid extraction.
dcm. it is insoluble in water also and has a greater density than water so will be on the bottom
If you ran out of diethyl ether, provide another suitable solvent that you could use for your extraction. Would the solvent you chose be a layer on top or bottom of the water?
no bc a drying agent can't have water and sodium sulfate pentahydrate contains 5 molecules of water
In the experiment you also used Sodium sulfate anhydrous. If you find that you have ran out of it, Could you use Sodium Sulfate pentahydrate instead? Why, or why not?
retention factor
It is a measurement of how high the compound traveled on a TLC plate and it is compared to the solvent front line
partition coefficient
It is a measurement of the solubility of a compound on the organic solvent and the aqueous solvent, it is specific for a particular compound and solvent
a
Nail polish remover is a common organic solvent mixture used by every day individuals, and these solvents are responsible for the strong odor of nail polishes. Nail polish remover is made up primarily composed of the following organic solvents: Acetone (bp = 56oC) Ethyl Acetate (bp = 77oC) Butyl Acetate (bp = 126oC) Identify the false statement below regarding this solvent mixture. a. Butyl acetate has the highest vapor pressure. b. If a bottle of nail polish is opened, acetone is the solvent you would smell most or first. c. If a bottle of nail polish remover was left open, butyl acetate would be the component most likely left in the bottle. d. In order to separate tese three components, you would need to use fractional distillation.
theoretical plate
One cycle of evaporation and condensation in a distillation.
c
Over 200 species of plants produce linalool, a terpene alcohol found in many flowers and spice plants. Linalool has multiple commercial applications, the majority of which are based on its pleasant scent (floral, with a touch of spiciness). At 20oC, 0.16 g of linalool acid dissolves in 100 ml of water, but 2.10 g of linalool dissolves in 100 ml of diethyl ether. What is the partition coefficient for linalool? a. 0.076 b. 2.1 c. 13.1 d. 42.1 e. 0.76
stationary phase
Phase that holds the compounds and whose interactions are interfered by the polar solvents
boiling chip
Small, irregularly shaped pieces of material (often made from such as alumina, calcium carbonate, porcelain or carbon) added to liquids to make them boil more smoothly.
vapor pressure
The pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature
evaporation
The process by which a liquid is converted into a vapor using latent (ambient) heat
boiling
The process where an external heating source is applied until the vapor pressure equals atmospheric pressure.
water
The solubility of a compound is 59 g per 100 mL in boiling methanol and 30 g per 100 mL cold methanol. It's solubility in water is 7.2 g per 100 mL at 95 oC and 0.22 g per 100 mL at 2 oC. Which solvent would be better for recrystallization? water or methanol
a
Two samples have the exact same melting points. Are they the same compound? What procedure could you perform to confirm this? a. Perform a "mixed" melting point = independently add each compound to a small amount of your sample and see if the melting point decreases. b. Slowly run two very precise melting points. c. Run a quick melting point for an approximate melting range, then a slow precise one. d. Run a very precise melting point and then run a fast one to double check your work.
london forces, dipole dipole
What are the intermolecular forces exhibited by caffeine?
3 15ml extractions
What is better, one 45 mL extraction, or three 15 mL extractions?
c
What is the purpose of adding Brine during an extraction? a. the presence of salt in the water layer decreases the solubility of the organic compound in the organic layer. b. the presence of salt in the water layer increases the solubility of the organic compound in the aqueous layer. c. the presence of salt in the water layer decreases the solubility of the organic compound in the aqueous layer.
a, b, c, d, e
What make a good extraction solvent? a. easily separate from compound after separation b. not react with the compounds c. exhibit high solubility for solute d. exhibit low solubility for unwanted compounds/impurities e. Be (almost) immiscible with other the solvent used f. be highly flammable
dcm has a low boiling point and if it't not cooled the dcm will begin to evaporate and the extraction won't be complete. some caffeine will be lost in the water
Why does the tea need to be cooled to room temperature before methylene chloride was added?
b
Why is it helpful to add sodium chloride added before extraction the aqueous layer with DCM? a. To make the sodium salt of caffeine and make it more soluble in water. b. To increase the dielectric constant of the water and make the caffeine choose DCM more readily. c. To help attract the caffeine into the water layer. d. To make the water more dense and become the bottom layer in the separation.
methanol is soluble in water so separation won't occur
Why is methylene chloride used for the extraction rather than methanol?
c
You prepare to perform a fractional distillation by packing a 10 cm fractionating column with glass beads. Which amount of glass beads will provide you the best separation during your fractional distillation? a. 50 mL glass beads b. 100 mL glass beads c. 200 mL glass beads d. 150 mL glass beads
fluorenone from fluorene
_______ was synthesized from _______ by air oxidation
flash point
________ for a flammable liquid is the min temp at which there are enough vapors of the liquid to ignite when an ignition source is brought near to it
hexane and toluene bc they have the largest diff in bp. fractional would be best bc its best when separating liquids of close bp
a mixture contains two of the following: hexane (bp=69), benzene (bp=80), 2-butanol (bp=99), and toluene (bp=110) which mixture of 2 compounds above will give the best possible separation between the 2 using distillation techniques. would you use simple or fractional distillation?
mobile phase
a pure solvent or a mixture of solvents
sublimation
a purification technique that involves a phase change (solid to vapor) allows the pure compound to be removed from impurities to produce a crystalline product. can be done under vacuum or at room temp
partially volatile, not react with compound being purified, have bp below mp of compound being purified
a suitable recrystallization solvent should be
the purification did not work completely. the anthranene is impure. impurities lower the melting point of a solid
after performing extraction, you take the melting point of your purified anthracene. the literature melting point of anthracene is 210-212 but you determine the melting point to be 196-2015. explain why youre melting point is low and what it means about your purification technique
na2so4
after you separate an organic phase from the water later, you might add a drying agent. what is a common drying agent
mobile phase
an eluting solvent that travels up tlc plate by capillary action
odd number
atoms that are affected by nmr must have an _______ of proton or neutron
1450-400
bending frequencies
simple distillation
benzene (80oC) from sodium hydride (solid, mp 800oC)
ir energy is absorbed by bonds when the energy of that bond is met. if that energy is met it shows up as an absorption in the spectrum. all wavelengths that don't match a bond energy transmit
briefly explain what occurs when ir energy interacts with a molecule. how is a spectrum achieved
aqueous phase
by deprotonating an acid it solubilizes in the ________
observe tlc
by eye if they are colored, or by the use of uv light, i2 stain, br2 stain (rarely), or other chemical stains that adhere to the compounds
organic phase
by protonating an acid or making a base neutral it will solubilize in the _______
aqueous phase
by protonating an amine (base) it solubilizes in the _______
steam distillation
cinnamaldehyde (bp 248 oC) from cinnamon
upside down tlc
column chromatography is
vapor pressure is the pressure above a liquid due to that liquid in the gas phase. higher vp=lower bp. hexane has the highest vp
describe what vapor pressure is and how it relates to a compounds boiling point. which compound hexane (bp=69), benzene (bp=80), 2-butanol (bp=99), and toluene (bp=110) has the highest vapor pressure
identification and purification
distillation is used for ___________
steam distillation
distillation of a liquid in a current of steam, used especially to purify liquids that are not very volatile and are immiscible with water. used for temp sensitive materials that tend to decompose at higher sustained temps
lower bp
does a lower or higher bp have a higher vapor pressure
decrease
does bp increase or decrease at higher altitudes
salting out
done by adding brine to the aqueous layer, it decreases the solubility of the organic compound in the aqueous phase allowing more of the organic compound to be transferred from the aqueous phase to the organic phase
when a mixture boils the vapor will be enriched in the compound with the lower boiling point, if the vapor condenses and evaporates again the vapor will be further enriched. each time this cycle continues the vapor becomes more pure in the lower boiling compound. a fractional distillation provides a larger surface area in which more of the cycles can take place allowing the vapor to become more pure each time
explain how fractional distillation column provides better separation what simple distillation
rapid cooling causes compound to precipitate out quickly trapping impurities in the crystals
explain why cooling the solution too quickly by immediately moving it from the hotplate to the icebath is a problem in recrystalization
more of your compound remains dissolved after recrystallization reducing your yield
explain why using a much larger volume of solvent than needed is a problem in recrystallization
sublimination
fast and easy way to purify several solids including caffeine
tlc
fast and efficient for the separation of small amounts of material and can be used to check the purity of lab samples, compare compounds for identity, follow the course of a reaction, separation, purification, etc
emulsion
formed in an extraction. a suspension of insoluble droplets of one liquid in another liquid. when formed the entire mixture has a milky appearance. disappears when allowed to sit for a few minutes
greater than 30-40
fractional distillation separates two components when bp is
by calculating the rf value and looking at the color characteristics
how can tlc be used to identify a compound
when the spot of the limiting reagent disappears
how to know when a reaction is complete on a tlc plate
gentle mixing
how to prevent emulsions
lower
impure solids generally melt at (higher, lower, the same) temp as a pure solid
ir radiation contains enough energy to stretch covalent bonds in organic molecules. the energy absorbed is particular to a given functional group.
in a couple sentences explain how the infrared energy is elated to the spectrum you observe. that is, what is going on when infrared energy in interacting with a molecule
polar compounds stick or adhere to the stationary phase through hydrogen bonding or less strongly through dipole-dipole interactions. chromatography allows you to employ increasingly more polar solvents until you entice the polar molecules
in all types of chromatography, compounds equilibrate between the mobile phase and a stationary phase. how does this allow for compounds to be separated? organic compounds adsorb to the stationary phase through intermolecular forces. what are the different types of intermolecular forces? what is the relative order of their strength
water
in an extraction involveing dichloromethane and water, which phase will be on top
more dense
in an extraction, what layer is always on the bottom
elution solvent
in liquid chromatography the mobile phase is
solid adsorbent with a liquid coating packed into a column
in liquid chromatography the stationary phase is
flammability, toxicity, expense
in selecting a good recrystallization solvent, one should also consider
2-3 seconds
in the distillation lab we wanted a drop every _______ seconds
it tells you the temperature of the vapor not the temperature of the boiling liquid
in the distillation lab what does the temperature you read on the thermometer tell you about the identity of the solvent
Infrared Spectroscopy
indicates functional groups present
molecular vibrations
infrared radiation is largely thermal energy. it induces stronger _______ in covalent bonds, which can be viewed as springs holding together two masses, or atoms
tlc
involved separation involving differential partitioning between a mobile and stationary phase
nmr
involves the study of the interaction between electromagnetic radion and the nuclei of atoms
dichloromethane
is caffeine more soluble in water or dcm
partition coefficient
k, Any organic compound with K>1.5 can be separated from water by an organic solvent. K = C1/C2 C1 = solubility of your compound in organic solvent C2 = solubility in water (aqueous) Notice that this value is independent of volume
fingerprint region
less than 1450 in IR
distillation
liquids are purified by
checking for purity, comparing 2 compounds for identity
list 2 uses for tlc
add a salt like nacl to the aqueous layer
list one way to prevent/remedy emulsions during an extraction
wear goggles, no eating drinking or chewing gum, wear gloves and remove when leaving lab
list three safety regulations that you must follow while in lab
hot filtration and recrystallization
mixture is heated up, when the compound is still soluble in the hot solvent the impurities are not and are then filtered out, filtrate is cooled down for the target compound to crystalize
low boiling points
most organic solvents used for extractions have _____ and may boil if added to a warm aqueous solution
nmr
most powerful and broadly applicable technique for structure determination
nmr
most powerful and broadly applicable technique for structure determination • Involves the study of the interaction between electromagnetic radiation (radio wave) and the nuclei of atoms • Atoms that are affected by NMR must have an odd number of proton (p+) or neutron (n).
toluene
naphthalene has a kD of 7.3 when extracting into toluene and a kD of 3.4 when extracting into hexanes. which solvent would you for extraction to reclaim the most of the compound
sources of confusion and common pitfalls in tlc
non horizontal bands (co-elute), channeling, loading sample too vigourously, column dry, crack
fractional distillation
pentane (36oC) and 2-propanol (83oC)
simple distillation
pentane (36oC) and toluene (110-111oC)
mobile phase
phase that pushes the compound up the silica gel on a tlc plate or down a column chromatography
vapor pressure
pressure of compound above its liquid or solid at a certain temp in a closed system
1. you may get sample or your hands contaminated 2. hand lotion can contaminate ir 3. you can get sick due to contamination by eating after
provide 3 viable reasons why you would need to wear gloves while using salt plates and taking an IR
mass spectroscopy
provides accurate molecular weight, gives fragmentation patterns to help piece molecule back together
c-o, c-s, c-se
put the following bonds in order from highest to lowest stretching frequencies
1. choose solvent 2. dissolve solute in hot solvent 3. cool solution to room temp slowly 4. collect crystals by filtration 5. wash crystals with cold solvent 6. dry crystals
recrystallization steps
chromatography
set of lab techniques for the separation of mixtures based on affinities
uv/visible spectroscopy
shows electronic transitions between orbitals
greater than 60-70
simple distillation separates two components when bp is
recrystallization
solids are purified by
4000-1450
stretching frequencies
partition coefficient
subtle differences in a compounds ____________ result in differential retention on the stationary phase, allowing the separation to be effective
mixed solvent recrystallization
target molecule is more soluble in one of the two solvents used, could be done modifying temps or not
nuclear magnetic resonance
tells environments and types of protons and carbons
more tightly
the ______ a compound binds to the stationary adsorbent the more slowly it moves on the tlc plate
distillation
the action of purifying a liquid by a process of heating and cooling.
polarities of the compounds in the mixture being separated
the appropriate composition of the mobile phase depends on ________
room temp
the aqueous solution needs to be at ______ before adding the organic extraction solvent
nacl
the clear disks used in sampling as thin films for ir spectroscopy are made of what materia
mobile phase, stationary phase
the mixture is dissolved in a fluid called the ____________ which carries it through the structure holding another material called the __________________
affect rf value
the solid adsorbant (silica gel vs alumina) the polarity of the compounds, the polarity of the solvent used
extract
the solution of the dissolved compounds in an extraction
immiscible
the solvent that is used for an extraction must be ________ with the other liquid
differential partitioning
the success of separation is based on ________________ between the mobile and stationary phase
their salts by adding sodium carbonate
the tannins in caffeine that are slightly soluble in dichloromethane can be eliminated by converting it to _______________
recrystallization from one solvent
the target compound should have high solubility at high temperatures. the impurity should have high solubility at low temps and either high or low solubility at high temps -hot filtration -cold filtration
extraction
the technique used to separate an organic compound from a mixture of compounds
boiling point
the temp at which the vapor pressure=external pressure (at 1 atm or 760 torr)
liquid compounds
tlc doesnt work well for ________ bc their volatility can lead to loss of the sample by evaporation
stationary phase
tlc plate made of a polar media, a thin layer of a polar solid such as silica gel or alumina, contains polar sites on the surface that adsorbs polar molecules by dipole-dipole and h-bonding interactions, is coated on an inert surface of a supporting material (glass, plastic, aluminum)
2x50 mL
to extract an organic material from an aqueous solution, would it be better to do one extraction with 100 mL ether or 2 extractions with 50 mL each of ehter
extraction
to pull out a compound from one layer into another
immiscible liquids
two liquids which are not soluble. when mixed they separate into two layers
column chromatography
upside down tlc, separates compounds in a larger scales, components: stationary phase (silica gel, alumina), mobile phase (mixed solvent, gradient elution)
melting point behavior
used to characterize purity and identity of solids by their mp range, a useful method for identification. Impure solids show a broadened (range widened) mp range and/or mp is depressed from expected literature mp.
stationary phase
usually polar-silica gel is most widely used
silica gel-sio2, alumina-al2o2
what are the two common stationary chromatography phases for tlc or column chromatography. what bonds are found in each respective stationary phase
density of solvent, temp of extraction mixture, preventing emulsions
what are things that need to be taken into account while carrying out an extraction
involves magnets
what does magnetic mean in nmr
nuclear magnetic reasonance
what does nmr stand for
in the nucleus
what does nuclear mean in nmr
uses radio frequency
what does resonance mean in nmr
molecular weight, surface area, increased polarity, stronger imf
what increases boiling point
that the dipole moment must change for the molecule
what is the one requirement for a bond stretch to show up in the ir
to separate bulk compound from eachother
what is the purpose of column chromatography
to remove trace h2o, when clumping stops or you get a snow globe effect
what is the purpose of the drying step and how do you know that you have added enough
sodium bicarbonate can neutralize both acids and bases that are still present. the gas building up is co2 as a byproduct
what is the purpose of using sodium bicarbonate in a workup extraction? what is the gas building up in your separatory funnel?
prevents pressure buildup and loss of solution
what is the reason for venting the separatory funnel in an extraction
heat the solution to remove excess solvent
what is the remedy if too much solvent is used in the recyrstallization process and no material crystallizes
characterization
what kind of technique is IR
separation
what kind of technique is extraction
purification
what kind of technique is recrystallization
purification
what kind of technique is sublimation
separation
what kind of technique is tlc
separatory funnel
what piece of specialized glassware is used in the lab to perform liquid-liquid extractions
Dichloromethane
what solvent was often used as an organic solvent in extractions
fractional, many vaporization condensation cycles take place and can efficiently separate components. more cycles helps make it more pure
what type of distillation is more efficient in the purification or separation of the two solvents
column chromatography
what was used to separate fluorenone and fluorene
higher
when distilling an ideal binary mixture of liquids through an efficient column the pot temp will be (higher, lower) than the head temp
nonpolar substances
when silica gel is the stationary phase the developing solvent moves ________ up the plate most rapidly
vent extraction mixture immediately
when using sodium carbonate or bicarbonate to extract or wash acidic contaminants from an organic solution __________ after the first inversion and subsequently after every 3-4 inversions
1665-2000
where is aromatic overtones in an arene
3200-3600 (broad)
where is the alcohol peak in an IR
2700
where is the aldehydic c-h in an aldehyde (there's 2 humps)
2100
where is the c-c triple bond in an alkyne
3000
where is the c-h bond in a nitrile
1100
where is the c-n bond in a primary amine
2200
where is the c-n triple bond in a nitrile
1600
where is the c=c in an alkene
1600
where is the c=c in an arene
1700
where is the c=o carbonyl in a IR
3300
where is the n-h bond in a primary amine (theres two humps)
3300
where is the n-h bond in a secondary amide (there's one and its longer)
3300
where is the n-h bond in a secondary amine (there's only one of them)
3300
where is the n-h in a primary amide (there's two and theyre longer)
at lower pressure the bp of liquid decreases. this is bc a liquid boils onces its vapor pressure=atmospheric pressure
while distilling 50 mL of aniline which you prepared in the lab, you record a bp of 184. the temp remains at this value throughout most of the distillation. however you talked to your friend who attends a university in denver colorado who performed the same experiment with a bp of 180. explain
carboxylic acid
wide oh peak mixed with sp3 c-h bond
polar solvents
will compete for polar sites on the adsorbent and cause faster migration of compounds up the plate
1. dissolve compounds in ether 2. extract aqueous with hcl-removes amino 3. extract aqueous with naoh-removes 2 napthoic 4. dry ether with na2so4 5. filter or decant 6. rotovap off ether
you are given a mixture containing 3 solids: anthracene, 2-napthoic acid, and 1-aminoaphthalene. describe procedure for getting pure solid anthracene by using extraction
melting point
you will collect a ________ to verify its purity and identity
extraction
• Topulloutacompound from one layer into another • Acompoundpartitions more toward where it is more soluble (equilibrium) • Partitioncoefficient • Multipleextractionsmay be needed to completely extract a substance
