Question 1

Which reaction sequence is used to lengthen an aldose carbohydrate chain by one carbon atom, and what is the key intermediate formed?

Accepted Answer

Kiliani-Fischer synthesis; forms a cyanohydrin intermediate

Question 2

What is the product of the following reaction sequence on D-glucose: $$\mathrm{1.\ $$NaBH_4$$,\ H_2O\ \rightarrow\ 2.\ Br_2$,\ H_2O}$$?

Accepted Answer

D-glucuronic acid

Question 3

Which of the following best describes the mechanism of peptide bond formation using DCC (dicyclohexylcarbodiimide)?

Accepted Answer

DCC activates the carboxyl group, allowing nucleophilic attack by the amino group to form an amide bond.

Question 4

Which sequence of reagents is used in the Wohl degradation to shorten an aldose chain by one carbon atom?

Accepted Answer

$$\mathrm{1.\ NH_2OH\ \rightarrow\ 2.\ Ac_2O\ \rightarrow\ 3.\ $$NaOCH_3$$}$$

Question 5

At physiological pH ($$\approx 7.4$$), what is the predominant form of an amino acid?

Accepted Answer

Zwitterion ($$\mathrm{NH_3$^+}$$ and $$\mathrm{COO^-})$$

Question 6

Which synthetic method would you use to prepare an amino acid from an aldehyde, ammonium chloride, and sodium cyanide?

Accepted Answer

Strecker synthesis

Question 7

What is the role of protecting groups such as Boc in peptide synthesis?

Accepted Answer

They prevent unwanted side reactions by temporarily masking reactive functional groups.

Question 8

Which of the following is a correct statement about the Hell-Volhard-Zelinsky reaction in amino acid synthesis?

Accepted Answer

It brominates the alpha carbon of a carboxylic acid, allowing substitution with ammonia to form an amino acid.

Question 9

Which of the following best describes the product of the Strecker synthesis starting from benzaldehyde?

Accepted Answer

Phenylalanine

Question 10

Which of the following statements about peptide bonds is FALSE?

Accepted Answer

Peptide bonds can freely rotate around the C-N bond.

Question 11

Which reagent is used to reduce an aldose to an alditol (sugar alcohol)?

Accepted Answer

$$\mathrm{$$NaBH_4$$}$$

Question 12

Which of the following is a key difference between the Kiliani-Fischer synthesis and Wohl degradation?

Accepted Answer

Kiliani-Fischer lengthens the carbohydrate chain; Wohl degradation shortens it.

Question 13

Which of the following best describes the structure of a peptide bond?

Accepted Answer

$$\mathrm{R_1$-CO-NH-R_2$}$$

Question 14

Which of the following amino acid forms is most prevalent at low pH (acidic conditions)?

Accepted Answer

Fully protonated ($$\mathrm{NH_3$^+}$$ and $$\mathrm{COOH})$$

Question 15

Which of the following is a correct sequence for the amidomalonate synthesis of an amino acid?

Accepted Answer

$$\mathrm{1.\ NaOEt\ \rightarrow\ 2.\ RBr\ \rightarrow\ 3.\ H_3O^+,\ heat}$$

Question 16

Which of the following statements about the Strecker synthesis is TRUE?

Accepted Answer

It involves the formation of an imine intermediate from an aldehyde and ammonia.

Question 17

Which of the following is the correct order of steps in the Wohl degradation?

Accepted Answer

Oxime formation, acetylation, base-induced elimination

Question 18

Which of the following best explains why only aldoses (not ketoses) undergo Kiliani-Fischer chain lengthening?

Accepted Answer

Aldoses have an aldehyde group that can react with HCN to form a cyanohydrin; ketoses do not.

Carbohydrate Chain Modification, Amino Acid Synthesis, and Peptide Bond Formation

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