Chemistry 211Name ______
Examination 4December 11, 1996
Each question is worth five points. Please write your answer on the examination booklet. There is only one correct answer for each question.
1.The reaction of a carboxylic acid and a primary amine to produce an N-alkyl amide can be classified as:
a)an addition reaction
b)a condensation reaction
c)an elimination reaction
d)a substitution reaction
2. A nucleophile is:
a)an electron rich reagent that attacks an electron deficient carbon atom
b)an electron deficient reagent that attacks a carbanionic site
c)an electron deficient reagent that induces homolytic cleavage
d)an electron rich reagent that effects a deprotonation of an acidic group
3. The C4H9Br isomer that is likely to react fastest with NaN3 in acetone is:
a)n-butyl bromide
b)s-butyl bromide
c)isobutyl bromide
d)t-butyl bromide
4. In the addition of HBr to 1-methylcyclohexene, the product that is expected, assuming that Markovnikov’s rule is obeyed is:
a)1-bromo-1-methylcyclohexene
b)cis-1-bromo-2-methylcyclohexane
c)trans-1-bromo-2-methylcyclohexane
d)3-bromo-1-methylcyclohexane
5. In order to calculate the enthalpy change for the following step of a proposed homolytic substitution,
I. + PhCH3 HI + PhCH2.
on would have to know:
a)the bond dissociation energies of I2, HI, a C-H bond of toluene and the C-I bond of benzyl iodide
b)the bond dissociation energies listed in part a) as well as the temperature at which the reaction is to be conducted
c)the bond dissociation energies of I2 and a C-H bond of toluene
d)the bond dissociation energies of HI and a C-H bond of toluene
6. In order to prepare CH3CH2CH2CN directly in an SN2 reaction, a possible starting material would be:
a)n-butyl bromide
b)n-propyl chloride
c)1-butanol
d)2-methyl-2-propanol
7. The energy change in a heterolytic reaction is:
a)calculated by including only the bonds which are broken
b)easier to calculate than in a homolytic cleavage because ions are produced
c)calculated by including only the bonds that are formed
d)harder to calculate than in a homolytic cleavage because solvation energy must be included
8. Retrosynthetic analysis is:
a)a return to the use of older methods for synthesizing a compound
b)a return to the use of biologically relevant synthesis routes
c)design of a series of reactions to accomplish a synthesis, working backward from a desired product
d)a main thrust of physical organic chemistry
9. The order of reactivity in SN1 reactions is a direct consequence of:
a)the stability of the key carbocation intermediate
b)the stability of the key free radical intermediate
c)steric hindrance to the approach of a nucleophile in the rate determining step
d)the requirement for backside attack in all nucleophilic substitutions
10. The reaction:
can be classified as
a)a rearrangement reaction
b)an elimination reaction
c)an addition reaction
d)a substitution reaction
11. Of the following, the reagent or sequence of reagents that converts 1-propyne to 2-butyne is:
a)H3O+ with H3COH
b)1. Ag(NH3)2OH; 2. CH3OH
c)1. NaNH2; 2. CH3Br
d)1. Zn; 2.CH3Br
12. The product expected from the following sequence is:
a)2-butanone
b)ethyl propanoate
c)acetoacetic acid
d)3-methyl-2-pentanone
13. In order to prepare a primary amine in synthetically useful yields from an alkyl bromide upon treatment with ammonia, it is important that:
a)a large excess of alkyl bromide is used
b)a 1:1 ratio of alkyl bromide and ammonia be used
c)a large excess of ammonia be used
d)none of the above
14. The product of the following malonic ester synthesis is:
a)1-methylpropanoic acid
b)2,2-dimethylpropanoic acid
c)ethyl-1-methylpropanoate
d)1,1-dimethylpropanoic acid
15. The Hell-Vollhard-Zelinski reaction is used to prepare:
a)primary amines uncontaminated by secondary or tertiary amine side products
b)iodoform and a carboxylic acid
c)-ketoacids
d)-bromocarboxylic acids
16. For the following reaction, predict the expected product. Where a center of chirality is created or destroyed, indicate the absolute configuration.
17. 2-Octanone has two sites for possible alkylation. Draw the structures of the two enolate anions that could be formed by treatment with sodium ethoxide.
18. Identify the organic halide that after conversion into a Grignard reagent and treatment with ethylene oxide would produce the following alcohol.
19. Propose a sequence of reactions and the appropriate reagents that can be used to effect the conversion of benzyl chloride into benzyl methyl ether.. If special conditions or solvents are needed specify them.
20.Using the reactions that you have learned suggest a route by which the 2-pentyne can be synthesized from a two or three carbon alkyne and any alkyl halide containing three carbons or fewer. You may use any other reagents needed; more than one step may be required.