CHEM 238 Lab Final Review 2019
In the reduction of camphor to isoborneol, sodium borohydride is used instead of lithium aluminum hydride because:
lithium aluminum hydride would react with the solvent ethanol
A KMnO4 test on the basic hydrolysis products of aspartame will detect the presence of
methyl alcohol
The first step in Fischer esterification is:
the protonation of the carbonyl oxygen of the carboxylic acid.
TLC is a technique used for:
the qualitative monitoring of reactions and evaluation of the purity of any compound
What should be done to neutralize a bromine or an iodine burn?
apply sodium thiosulfate solution
Which of these is true about thermodynamic and kinetic control?
-For most reactions, kinetic and thermodynamic products are the same -In thermodynamic control, the product ratio depends on the relative stability of the products -In kinetic control, the product ratio depends on the relative energies of the transition states -In some reactions, the less stable product is formed at a faster rate
Which of the following is false:
-There is no way to control the outcome of a reaction in which the kinetic and thermodynamic products are different. -It always produces the most stable product -Kinetic products always go through a higher energy transition state -The kinetic product is always the slowest to form -The thermodynamic product is higher in energy than the kinetic product
Theoretically, how many moles of a ketone can reduce one mole of sodium borohydride?
4
In order to determine whether the desired product type was produced in the Grignard reaction, you obtained an IR spectrum. Them main peak that should have been absent was at approximately:
1700-1720 cm-1
A Grignard reaction of n-butylmagnesium bromide with acetone would produce:
2-methyl-2-hexanol
Which of the following compounds would give a negative iodoform test?
2-methylbutanal
In the addition of the HBr to butadiene, which product is the product of kinetic control?
3-bromo-1-butene
What is the UVA range of light?
315-400 nm
In order to determine whether the desired type of functional group was produced in the Grignard reaction, you obtained an IR spectrum. The characteristic peak that should have been present for the product was at approximately:
3200-3600cm-1
Based on your lab experience, if you form the same reaction using salicylic acid in the place of salicylamide, which of the following would be produced as the major product?
5-iodosalicylic acid
What is the key IR stretch for the aromatic substitution pattern of 5-iodosalicylamide?
850-800cm-1, 1,2,4-trisubstituted
The Beer's law formula is:
A= EPC
Choose the correct statement that compares the reactivity of acetanilide to ethylbenzoate toward electrophilic aromatic substitution.
Acetanilide is more reactive toward electrophilic aromatic substitution owing to the electron-donating group attached to the aromatic ring.
Isopentyl acetate has a pleasant smell of bananas. What two reagents can this ester be made from?
Acetic acid and isopentyl alcohol
Substituents on an aromatic ring affect electrophilic aromatic substitutions in that:`
Activating groups make substitution more likely by donating electron density.
Which of the following statements is false about Grignard Reaction?
Alcohols are often used as solvents in Grignard Reactions
One resonance form of a delocalized allylic cation is shown. Which carbon of this cation will have the greatest positive charge?
C2
The organic product produced when benzaldehyde is reacted with Tollens' reagent is present in solution in the form:
C6H5CO2- NH4+
Amide bonds in polypeptides can be easily hydrolyzed under acetic or basic conditions. Select the letter that represents the amide bond.
C: The amide bond is the bond between the carbonyl carbon and nitrogen in the polypeptide chain.
The precipitate observed in a positive iodoform test is:
CHI3
Which of the following substituents of an aromatic ring are electron-withdrawing?
Carbonyl and nitro groups
Which of the following is not a polyamide?
Cotton
Which of the following polymers is a polyester comprising of identical repeating units?
Dacron 54
Upon heating, aspartame rearranges to form a cyclic compound known as __________.
Diketopiperazine
Which of the following statements is not correct?
Esters, acid chlorides, ethers and amides are all derivatives of carboxylic acids.
In the borohydride reduction of camphor, NaBH4 provides __________ to reduce camphor
H-
Benzoyl chloride can react with water in your eye. What is a product of his reaction, and what risky substance is benzoyl chloride classified as?
HCl, lachrymator
What species is responsible for generating the diazonium intermediate during the synthesis of the azo-dye?
HNO2
Why do we need to convert indigo to leucoindigo to dye a fiber?
Indigo is not water-soluble.
What is true of alpha-helix secondary structures?
Involve hydrogen-bonding interaction between amino acid groups that are 4 residues apart on the same chain
Which of the following amino acids is classified as basic?
Lys and His
The active site of Mandelate racemace involves the presence of a non-protein species in the active site to which you measured some bond distances. That species (called a prosthetic group) was:
Mg 2+
Why do esters, which have higher molecular weights than carboxylic acids, have lower boiling points than the carboxylic acids they were made from?
Most carboxylic acids exist as dimers which are held together by two hydrogen bonds.
Which of the following reagent(s) can be used to reduce camphor in ethanol?
NaBH4
Which pair of reactants is responsible of the formation of the azo salt in the diazonation of an aromatic primary amine?
NaNO2 and HCl
Which of the following stains was used in the peptide and amino acid lab on the TLC plate?
Ninhydrin
Which test is used most often to detect the presence of amino acids?
Ninhydrin test
The aldol reaction between dibenzyl ketone and benzil is synthetically useful because of which of the following?
One of the compounds has no alpha-hydrogens.
What is the classification of an enzyme?
Protein
The equilibrium reaction of a Fischer esterification can be shifted to yield more ester by:
Removal of water
Which of the following items is false about the UV analysis of sunscreens experiment?
SPF only refers to product effectiveness against the UVA rays of the sun.
In the iodination of salicylamide, what reagent was acting as the nucleophile in this reaction?
Salicylamide
Which one is not a derivative of carboxylic acids?
Schiff's Base
The reaction of a Grignard reagent with most aldehydes produces a __________ alcohol and the reaction of a Grignard reagent with a ketone produces a __________ alcohol.
Secondary, tertiary
Which method is used to determine the structure of an enzyme?
Single-crystal x-ray crystallography
In the aldol condensation experiment a computer was used to analyze the TPCP molecule. One of the questions asked was why the molecule is not completely planar. What prevents this molecule from being planar?
Steric interactions between the phenyl groups.
Which of the following statements is true?
The Tollens' test is positive for both hexanal and benzaldehyde.
The hydrolysis of esters can be done by both acid or base catalysis, however esterification of carboxylic acids can only be done by acid catalysis. Why is this?
The carboxylic acid will be deprotonated by the base and will leave an unreactive carboxylate anion.
Which of the following statements about TPCP, the product in the aldol experiment, is true?
The phenyl rings of TPCP are twisted with respect to the plane of the cyclopentadienone ring, and each phenyl is twisted in the same direction as the others.
Which of the chemical tests listed below could be used to distinguish between benzaldehyde and phenylacetone?
Tollens' test and Iodoform test
Avobenzone and oxybenzone are sunscreen ingredients that both protect against __________ rays.
UVA and UVB
SPF refers to product effectiveness against the __________ rays of the sun.
UVB
Which of the following may give you a false positive result in 2,4-DNP test?
Washing the glassware with acetone without letting it evaporate.
The major product of the reaction of camphor with NaBH4 is formed when:
a borohydride ion makes an endo attack at the carbonyl to form the exo product
Which of the following observations is the best evidence that an unknown compound is an aldehyde?
a silver mirror in Tollens' test
How could you have used infrared spectroscopy to determine if the sodium borohydride reduction of camphor had gone to completion?
absence of a peak at 1746 cm-1 and presence of a peak at 3500 cm-1
To prepare 2-methyl-2-pentanol from a Grignard reaction, you need to use __________ and __________ as starting material.
acetone, 1-bromopropane
The ceric nitrate test is used to detect the presence of
alcohols
Which class of compounds is most resistant to hydrolysis (i.e. requires more time and harshest reaction conditions)?
amides
Amides can be prepared in one step by reacting an amine with
an acid chloride
What is the intermediate formed during the reaction of an aldehyde and base in the first step of an aldol condensation?
an enolate
The imidazole functional group of histidine is an enzyme active site can act:
as a base to remove a proton from a substrate and as an acid to donate a proton to a substrate
Aspartame is one of the most common alternatives to sugar. It is a dipeptide of __________.
aspartic acid and phenylanaline
In the reduction of ketones, an excess of sodium borohydride is usually used:
because borohydride reacts slowly with the solvent
What is the name of the ester prepared from propanoic acid and butyl alcohol?
butyl propanoate
Which is the general category of compounds that are the common active ingredients in sunscreens?
conjugated aromatic compounds
In an aldol condensation, the reactive intermediate generated by the reaction of a carbonyl compound with a strong base is an __________, which acts as a __________ toward another carbonyl compound.
enolate, nucleophile
When camphor is reduced by sodium borohydride:
isoborneol, the exo product formed through the endo attack of the hydride is the major product.
A student spills concentrated sulfuric acid on their hand, what should the student do?
go to the sink and begin running water over the affected area, while your lab partner notifies the TA
To obtain the UV spectrum of sunscreen ingredients, we dissolved the samples in:
isopropyl alcohol
Which of the following is the least volatile?
methyl salicylate
In the coupling reaction between the diazonium salt and the phenol compound in the Azo dye experiment the phenol acts as a(n):
nucleophile
Functionally, proteins are
polymeric peptides
A catalytic amount of mineral acid in Fischer esterification of a carboxylic acid:
protonates the carbonyl oxygen of the carboxylic acid, generating a reactive, resonance stabilized electrophilic species
What type of derivatives are prepared from ketones and aldehydes?
semicarbazones and 2,4-dinitrophenylhydrabenzones
Aspartame is used as a __________. People that have the metabolic disorder, PKU, should restrict their intake of aspartame because they lack the enzyme needed to metabolize __________.
sweetener; phenylanaline
A mixture of nitric acid and sulfuric acid was added to an equimolar mixture of C6H6, C6H5Z, C6H5Y. After warming and stirring for a few minutes the nitrated products were analyzed and found to consist of the products C6H4YNO2, C6H5NO2, and C6H4ZNO2 in the ratio of 750:30:1, respectively. This data allows one to conclude that:
the Y group is an activator
Which of the following statements is not true?
the affinity of a dye for a particular fabric depends only on the fabric's structure
Electrophilic substitution of methyl benzoate occurs meta to the substituent because:
the electron withdrawing ester group destabilizes the ortho and para positions more than the meta position
A possible cause for a Grignard reaction failing to initiate is the:
use of magnesium with heavy oxide layer