CHEM 238 EXAM 2025 QUESTIONS AND
ANSWERS
Which of the following is a suitable reagent that will quickly distinguish between pentanal and
3‐
pentanone?
a. Br2/CCl4
b. Ag(NH3)2+ OH-
c. NH2OH
d. 2,4‐DNP
e. Na metal - ANS b. Ag(NH3)2+ OH-
In the aldol condensation, the base:
a. solubilizes the transition state
b. attacks the carbonyl to form the condensation product
c. abstracts the hydrogen on the carbonyl carbon
d. abstracts the hydrogen alpha to the carbonyl
e. acts as a oxidizing agent - ANS d. abstracts the hydrogen alpha to the carbonyl
What type of bond links amino acids together to make peptides?
a. a hydrogen bond
b. an ionic bond
c. an amide bond
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, d. a carbon ‐ carbon bond
e. none of these - ANS c. an amide bond
Ammonolysis of benzoyl chloride with cold concentrated ammonium hydroxide produces:
a. benzoic anhydride
b. benzamide
c. benzonitrile
d. benzanilide
e. dibenzyl ketone - ANS b. benzamide
A method to make a primary alcohol with a Grignard reagent (R‐MgX) is to react the Grignard
reagent with:
a. a symmetrical ketone R2CO
b. an aldehyde R‐CHO
c. an ester R‐CO2R'
d. formaldehyde H‐CHO
e. an unsymmetric ketone R‐CO‐R' - ANS d. formaldehyde H‐CHO
12. Which is the best reagent for detecting amino acids on TLC plate?
a. a ninhydrin solution
b. a potassium permanganate solution
c. a ceric ammonium nitrate solution
d. Schiff's reagent
e. Dragendorff's reagent - ANS a. a ninhydrin solution
Which of the following UV rays can penetrate the earth's atmosphere?
UVA UVB UVC
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, I. II. III.
a. I only
b. I and II
c. II and III
d. I and III
e. I, II, and III - ANS b. I and II
How are triazine herbicides prepared?
a. electrophilic aromatic substitution
b. SN2
c. nucleophilic aromatic substitution
d. dehydrohalogenation
e. SN1 - ANS c. nucleophilic aromatic substitution
Which among the derivatives of carboxylic acids are the least reactive towards hydrolysis?
a. esters
b. acid anhydrides
c. acid chlorides
d. acid bromides
e. amides - ANS e. amides
The Grignard reagent, n‐butylmagnesium bromide, may be classified as a:
a. carbon electrophile
b. carbon acid
c. reactive free radical
d. carbocation
e. carbon nucleophile - ANS e. carbon nucleophile
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ANSWERS
Which of the following is a suitable reagent that will quickly distinguish between pentanal and
3‐
pentanone?
a. Br2/CCl4
b. Ag(NH3)2+ OH-
c. NH2OH
d. 2,4‐DNP
e. Na metal - ANS b. Ag(NH3)2+ OH-
In the aldol condensation, the base:
a. solubilizes the transition state
b. attacks the carbonyl to form the condensation product
c. abstracts the hydrogen on the carbonyl carbon
d. abstracts the hydrogen alpha to the carbonyl
e. acts as a oxidizing agent - ANS d. abstracts the hydrogen alpha to the carbonyl
What type of bond links amino acids together to make peptides?
a. a hydrogen bond
b. an ionic bond
c. an amide bond
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, d. a carbon ‐ carbon bond
e. none of these - ANS c. an amide bond
Ammonolysis of benzoyl chloride with cold concentrated ammonium hydroxide produces:
a. benzoic anhydride
b. benzamide
c. benzonitrile
d. benzanilide
e. dibenzyl ketone - ANS b. benzamide
A method to make a primary alcohol with a Grignard reagent (R‐MgX) is to react the Grignard
reagent with:
a. a symmetrical ketone R2CO
b. an aldehyde R‐CHO
c. an ester R‐CO2R'
d. formaldehyde H‐CHO
e. an unsymmetric ketone R‐CO‐R' - ANS d. formaldehyde H‐CHO
12. Which is the best reagent for detecting amino acids on TLC plate?
a. a ninhydrin solution
b. a potassium permanganate solution
c. a ceric ammonium nitrate solution
d. Schiff's reagent
e. Dragendorff's reagent - ANS a. a ninhydrin solution
Which of the following UV rays can penetrate the earth's atmosphere?
UVA UVB UVC
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, I. II. III.
a. I only
b. I and II
c. II and III
d. I and III
e. I, II, and III - ANS b. I and II
How are triazine herbicides prepared?
a. electrophilic aromatic substitution
b. SN2
c. nucleophilic aromatic substitution
d. dehydrohalogenation
e. SN1 - ANS c. nucleophilic aromatic substitution
Which among the derivatives of carboxylic acids are the least reactive towards hydrolysis?
a. esters
b. acid anhydrides
c. acid chlorides
d. acid bromides
e. amides - ANS e. amides
The Grignard reagent, n‐butylmagnesium bromide, may be classified as a:
a. carbon electrophile
b. carbon acid
c. reactive free radical
d. carbocation
e. carbon nucleophile - ANS e. carbon nucleophile
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