CHEM 238 EXAM 2025 QUESTIONS AND
ANSWERS
Which of the following is a suitable reagent that will quickly distinguish between pentanal an 3-
pentanone? - ANS Tollen's Reagent (Tollen's test takes advantage of the relative ease of
oxidation of an aldehyde to a carboxylic acid..silver(I) dissolved in aqueous ammonia. pg 97 of
manual)
In the aldol condensation, the base: - ANS is the first step of the base catalyzed by
mechanism, a hydroxide (base) ion abstracts one of the alpha-hydrogens to produce the
enolate. (pg 285)
Choose the correct statement that compares the reactivity of acetanilide to ethylkbenzoate
toward electrophilic aromatic substituion (EAS) - ANS Acetanilide is more reactive toward
EAS owing to the electron donating group attached to the aromatic ring.
(carbonyl, sulfonyl, nitrile, or nitro substituents act as strong electron withdrawing groups,
reducing the electron density of the aromatic ring and dramatically lowering its reactivity, pg.
204)
What type of bond links amino acids together to make peptides? - ANS An amide bond
(amine terminal group of one amino acid bonds to the carbonyl terminal group of a second
acid, thus forming an amide bond.)
The fisher esterifaction of benzoic acid with methanol yields ethyl benzoate (ester) as the
product. Which of the following intermediates is involved in the formation o fethyl benzoate? -
ANS (protanation of the oxygen of the carbonyl activates the carbonyl carbon, which
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, undergoes nucleophilic attack by a molecule of the alcohol to produce a tetrahedral
intermediate. Pg 270)
In the organic labe you synthesized simazine ( a herbicide) by the reaction below. which of the
following is simazine? - ANS Review Tiazine Herbicide lab ( Substiution of two chlorine atoms
of cyanuric chloride with two ethylamine groups yields simz)
Which of the following is a Claisen Head adapter - ANS Fig. on page 248 of lab manual
Ammonolysis of benzoyl chloride with cold concentrated ammonium hydroxide produces: -
ANS Benzamide ( lab manual doesn't say, from lecture, acid chlorides are extremely reactive
and can thus be converted to less reactive carboxylic acid derivatives. Nucleophilic attack by
ammonia displaces the chlorine, forming a N-C=O bond, otherwise known as an amide.)
A method to make a primary alcohol with a Grgnard reagent (R-MgX) is to react the grignard
reagent with: - ANS Formaldehyde H-CHO (Reactio with formaldehyde produces a primary
alcohol that has a carbon chain one carbon longer that the beginning Grignard reagent, Pge 244
NOTE: reactions with ketones yield tertiary alcohols, and reaction with aldehydes yield
secondary alcohols.)
Which is th product of the aldon condensation o fcyclopentanone? - ANS alpha-beta alkene
prduct (Aldol reaction yieldsa beta-hydroxy product. removal of water (condensation) frmo the
product produces an alpha-beta alkene product.)
Remember that a single resonance-stabilized compoun or intermediate may be represented by
any of the individual hybrid structures. How many differnt cationic intermediates are
represented by the structures below? - ANS 4 (If you rearrange the last two carbocation
resonance structures, they are the same. thus there are four differnt cationic intermediates.)
Which is the best reagent for detecting amino acids on TLC plate? - ANS A ninhydrin solution
("in the experiment today you will examine aspartame, phenylalanine, and aspartic acid by TLC
using ninhydrin a sthe visualtation indicator" pg 314. "Ninhydrin is the best know of all the tests
for the presence of amino acids" pg 93)
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ANSWERS
Which of the following is a suitable reagent that will quickly distinguish between pentanal an 3-
pentanone? - ANS Tollen's Reagent (Tollen's test takes advantage of the relative ease of
oxidation of an aldehyde to a carboxylic acid..silver(I) dissolved in aqueous ammonia. pg 97 of
manual)
In the aldol condensation, the base: - ANS is the first step of the base catalyzed by
mechanism, a hydroxide (base) ion abstracts one of the alpha-hydrogens to produce the
enolate. (pg 285)
Choose the correct statement that compares the reactivity of acetanilide to ethylkbenzoate
toward electrophilic aromatic substituion (EAS) - ANS Acetanilide is more reactive toward
EAS owing to the electron donating group attached to the aromatic ring.
(carbonyl, sulfonyl, nitrile, or nitro substituents act as strong electron withdrawing groups,
reducing the electron density of the aromatic ring and dramatically lowering its reactivity, pg.
204)
What type of bond links amino acids together to make peptides? - ANS An amide bond
(amine terminal group of one amino acid bonds to the carbonyl terminal group of a second
acid, thus forming an amide bond.)
The fisher esterifaction of benzoic acid with methanol yields ethyl benzoate (ester) as the
product. Which of the following intermediates is involved in the formation o fethyl benzoate? -
ANS (protanation of the oxygen of the carbonyl activates the carbonyl carbon, which
1|P a g e C o p y r i g h t © 2 0 2 5 T H E B R I G H T A L L R I G H T S R E S E R V E D
, undergoes nucleophilic attack by a molecule of the alcohol to produce a tetrahedral
intermediate. Pg 270)
In the organic labe you synthesized simazine ( a herbicide) by the reaction below. which of the
following is simazine? - ANS Review Tiazine Herbicide lab ( Substiution of two chlorine atoms
of cyanuric chloride with two ethylamine groups yields simz)
Which of the following is a Claisen Head adapter - ANS Fig. on page 248 of lab manual
Ammonolysis of benzoyl chloride with cold concentrated ammonium hydroxide produces: -
ANS Benzamide ( lab manual doesn't say, from lecture, acid chlorides are extremely reactive
and can thus be converted to less reactive carboxylic acid derivatives. Nucleophilic attack by
ammonia displaces the chlorine, forming a N-C=O bond, otherwise known as an amide.)
A method to make a primary alcohol with a Grgnard reagent (R-MgX) is to react the grignard
reagent with: - ANS Formaldehyde H-CHO (Reactio with formaldehyde produces a primary
alcohol that has a carbon chain one carbon longer that the beginning Grignard reagent, Pge 244
NOTE: reactions with ketones yield tertiary alcohols, and reaction with aldehydes yield
secondary alcohols.)
Which is th product of the aldon condensation o fcyclopentanone? - ANS alpha-beta alkene
prduct (Aldol reaction yieldsa beta-hydroxy product. removal of water (condensation) frmo the
product produces an alpha-beta alkene product.)
Remember that a single resonance-stabilized compoun or intermediate may be represented by
any of the individual hybrid structures. How many differnt cationic intermediates are
represented by the structures below? - ANS 4 (If you rearrange the last two carbocation
resonance structures, they are the same. thus there are four differnt cationic intermediates.)
Which is the best reagent for detecting amino acids on TLC plate? - ANS A ninhydrin solution
("in the experiment today you will examine aspartame, phenylalanine, and aspartic acid by TLC
using ninhydrin a sthe visualtation indicator" pg 314. "Ninhydrin is the best know of all the tests
for the presence of amino acids" pg 93)
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