Ocher Lab 2545

an intensive property is

a property of matter that does not change as the amount of matter changes

azobenzene is

neither an amine nor an organic acid

in order to remove the insoluble solid impurity during your recrystallization, you will perform a _____ using a _____

vacuum filtration, Buchner funnel

rank the intermolecular forces from weakest to strongest ionic, dipole-dipole, van der Waals, hydrogen bonding

van der Waals, dipole-dipole, hydrogen bonding, ionic

melting points are ___ _______ to impurities

very sensitive

True or false: acid-base reactions require both an acid and a base, if an acid is added to an acid, there will be no reaction

True

True or false: the pKa of a protonated cyclohexyl amine is 10.7. at a pH of 2, the amine is still primarily protonated

True

a good separation is achieved when each compound has

a different Rf value

the S,S-isomer and R,R-isomer of the same compound are

a pair of enantiomers

The bronsted-lowry definition of a base is a species that

accepts a proton

the R,S-isomer of a symmetrical molecule is

achiral and meso

pKa is an indicator of the strength of an

acid

the _____ the pH, the lower the hydrogen ion concentration and the ____ acidic the solution

higher, less

when 2 ____ solvents come into contact, they separate into 2 layers according to their densities. The top layer will be ____ dense than the bottom layer.

immiscible, less

________ are intermolecular forces resulting from electron density around one molecule influencing the electron density around another

induced dipole-dipole forces

1-bromobutane and 1-butanol are

irritants and flammable

what letter represents the rate constant?

k

what do you need to assemble a reflux apparatus

large screw cap with a hole, round-bottom flask, stir bar, water condenser, large o-ring

at a pH ___ than the pka, the acidic form dominates

less

qualities of a good recrystallization solvent

low boiling point, nontoxic, inexpensive, inert

to determine which compound will get deprotonated, we look at which compound has the ____ pka

lower

the _____ the pH, the higher the hydrogen ion concentration and ____ acidic the solution

lower, more

when naming alkyl halides, the parent chain is numbered in the direction that gives the substituents the ____ possible numbers, and the substituents are listed in ____ order

lowest, alphabetical

to be chiral, a molecule

may not contain a mirror plane, must be non-superimposable with a mirror image

What intensive properties were measured in lab 2 to identify the solid unknown?

melting point

during lab 5 (addition rxns) you will use _____ to tell which product you obtained

melting point

compounds that contain more than one chiral center and have an internal plane of symmetry are called

meso

alkyl halide reactivity most to least relative (1-4)

methyl, primary, secondary, tertiary

isomers are molecules that have the same ____ but are ____

molecular formula, not identical

reactions involving negatively charged nucleophiles occur _____ rapidly in _____ solvents such as DMSO

more, polar-aprotic

in liquid chromatography, components of a mixture are separated by partitioning between a _____ liquid phase and a solid _____.

moving, adsorbent

Is hexane polar or non polar?

non polar

if you add sodium sulfate to your product and after 5-10 min the solid is clumped, this indicated your sample is ____ and you should_____

not dry, add more sodium sulfate

in an Sn2 reaction the _____ replaces the _____

nucleophile, leaving group

the Sn2 reaction is a ____ -step reaction and the reaction rate depends on the concentration of the _____

one, nucleophile and the electrophile

in an Sn2 reaction, the nucleophile approaches the carbon atom from the ____ side as the leaving group

opposite

generally, extractions involve an ____ phase and an aqueous phase

organic

to name branches alkanes, you should begin by finding the longest carbon chain. this is the ____ chain

parent

the henderson-hasselbalch equation shows the relationship between ____ and _____

pka, pH

using the ABBE refractometer, it is important to

place your liquid sample on the prism with a clean plastic pipette, only turn the dials you are instructed to turn, wipe the glass with a swab of cotton dampened with ethanol

a carbocation is

planar (usually sp2 hybridized)

Is ethyl acetate polar or non polar?

polar

carbocation stability from least to most stable (1-3)

primary, secondary, tertiary

another term for an acid-base reaction is a

proton transfer

TLC is primarily a tool for rapid ______ analysis

qualitative

________ is the purification technique you will use to remove impurities from your solid unknown

recrystallization

The ABBE refractometer measures?

refractive index

Sn1 reactions occur faster or slower in non-polar solvents?

slower

examples of goof TLC techniques

solvent level in the TLC chamber below the spotting line, spot on spotting line should be small, the TLC chamber should be left closed when developing a plate

the hydroxide ion is a _____ base and therefore a ______ leaving group. by protonating the -OH group with the acid catalyst, you can convert it into ____ which is a better leaving group

strong, poor, water

______ bases are better nucleophiles

stronger

the lower the pka the _____ the acid

stronger

the pKa of benzoic acid is 4.17. the pKa of HCl is -7. this means that HCl is a ____ acid than benzoic acid

stronger

What does each letter in the Sn1 reaction stand for?

substitution, nucleophilic, unimolecular

in this reaction what is the acid catalyst?

sulfuric acid

the rate of an Sn1 reaction depends upon the concentration of _____

the alkyl halide

the rate of an Sn2 reaction depends upon the concentration of ______

the alkyl halide and the nucleophile

the rate-determining step of the Sn1 reaction is

the formation of the carbocation

which process directly causes the color change of the reaction indicator in lab 8?

the generation of an acid

In a solvolysis reaction what is the solvent molecule?

the nucleophile

prefixes di-tri, and tetra- are used in naming when

the same group appears more than once

What is TLC used for?

to identify a compound by comparing to a standard, to test the completeness of a reaction, to get a rough estimate of the purity of a product

What is the role of capillary action in TLC?

to move the liquid phase up the plate

in an eclipsed conformation, the forces contributing to the higher energy state include: _____ strain- the repulsion of bonded electrons when the come close to each other -and _____ strain- the repulsion between the electron clouds of atoms or groups of atoms

torsional, steric

True or false: when 2 miscible solvents come into contact, they do not separate into 2 layer

true

during a halogenation reaction, a molecule of bromine adds to an alkene to produce a ______ dihalide, which is a compound with halogens bonded to adjacent carbons

vicinal

all are examples of intensive properties EXCEPT volume, density, boiling point, molecular weight

volume

in general, salts are soluble in ___ and neutral (uncharged) organic molecules are soluble in ___

water, organic solvents

good leaving groups are ____ bases

weak

water is an example of a ____ base, this makes it a ____ leaving group, but a _____ nucleophile

weak, good, poor

_____ bases make the best leaving groups because they are stable in solution as their anions, therefore the _____ the base, the faster it will react as a leaving group

weak, weaker

the stronger the acid the _____ its conjugate base

weaker

How do you tell when the reaction is complete for lab 8?

when the color changes to yellow

Tailing on a TLC plate is?

when the spot has a tail behind it

Bromocresol green at a pH below 3.8 is?

yellow

How to calculate an Rf value?

(it is constant under a set of conditions) calculated by dividing the distance the compound traveled by the distance the solvent traveled Rf = dot/ solvent line

What is a nucleophile?

An electron pair donor (has an available pair of electrons to donate to form a bond)

alkyl branches off of a parent chain are named by replacing the -ane ending with ___

-yl

if the bromination of a symmetrical, cis-alkene proceeded through a sin-addition, (#) different products are formed, the products would be _____

1, a meso-compound

mixed melting point is a technique used to determine the identity of an unknown solid. _____ % of a _______ compound is added to an _______ sample. If it the melting points match there us evidence the compounds are the same.

10, known, unknown

an Sn1 reaction is a ____-step reaction

2

if the bromination of a symmetrical, cis-alkene proceeded through a bromonium ion intermediate, (#) different products are formed, the products would be _____

2, a pair of enatiomers

if the bromination of a symmetrical, cis-alkene proceeded through a carbocation intermediate, (#) different products are formed, the products would be _____

3, a pair or enantiomers and a meso-compound

the pKa of cyclohexyl amine is 10.7. this means that at a pH of 10.7, cyclohexyl amine is

50% protonated and 50% neutral

The oxonium ion has what?

a cross of carbons with an O with 2 H attached to it and a proton on the oxygen

If a compound does not appear visible to the eye, it can be seen if they absorb _____ light. The plates are coated in a ____ chemical and when a plate is exposed to _____, the compounds will appear as _____ spots because they ______ the light.

UV, fluorescent, UV light, dark, absorb

halogenation are _____ reactions

addition

On a TLC plate, less polar substances generally _______ the plate than the more polar substance

advance further up

examples of solid adsorbents used in liquid chromatography

alumina, silica gel, cellulose

m-nitroaniline is a(n)

amine

benzoic acid is

an organic acid

tailing on a TLC plate can result from

application of too much compound on the spotting line, a compound slowly decomposing on the plate

a meso-compound must have

at least 2 chiral centers and a plane of symmetry

in an Sn2 reaction, bond breaking and bond forming are concerted, which means they occur _____

at the same time

What do you return to the stockroom at the end of the unknown lab 2?

automatic pipette

At the end of lab 8 what items will be returned to the stockroom?

automatic pipette and digital timer

____ will deprotonate ____ to form salts of organic acids, these salts are soluble in____

bases, acids, water

in a liquid-liquid extraction an extracting solvent must:

be immiscible with the original solvent, dissolve the solute better than the original solvent

boiling point of the solvent must be ______ (above/below) the melting point of the solid to prevent _____

below, oiling out

Bromocresol green at a pH above 5.4 is?

blue

all techniques used to characterize the alkyl halide product

boiling point, density, beilstein test

in a reflux apparatus water flows in the bottom or the top?

bottom (out through the top)

when naming molecules, ____ are used between numerals, and ____ are used between numerals and letters

commas, hyphens

In an acid-base reaction, the species that has an extra proton in the products is the

conjugate acid (from the base in reactants)

In a acid-base reaction, the species that has one less proton in the products is the

conjugate base (from the acid)

____ isomers- also known as structural isomers- have the same molecular formula but differ in the order that the atoms are attached

constitutional

for the flame test, you drip a ____ wire into your sample, when the wire is heated a ____ flame indicates there is a _____ present

copper, green, halogen

pyridinium tribromide is

corrosive and a lachrymator (irritates eyes and causes tears to flow)

the presence of an impurity will _____ the melting point and _____ the melting point range

decrease, widen

A solid is dissolved in a hot recrystallization solvent. Solubility of the solute (inc/dec). Recrystallization needs to happen (fast/slow ) and is important to make sure _______ is excluded

decreases, slowly, impurities

a molecule containing one chiral center exists as a pair of non-superimposable mirror images, or

enantiomers

melting is an _______ process

endothermic

vaporization is the phase change from liquid to vapor and is an _______ process. Boiling is an example of a _____ change.

endothermic (energy added to system), physical

If a substituent is axial and the structure undergoes a ring flip, the substituent would then be ______

equatorial

True or false: a neutral compound will react with an acid

false

True or false: salts of amines are soluble in organic solvents

false

a chiral carbon is a carbon bonded to ____ different groups

four

Bromocresol green at a pH between 5.4 and 3.8 is?

green

a straight chain alkane with the molecular formula C7H16 is called

heptane

the _____ (higher/lower) the compounds affinity for the solid phase relative to the liquid phase, the slower the compound will move through the adsorbent

higher

the more polar a substance the (higher/lower) it will move on the plate

higher