Q.56 Which of the following amino acids contain(s) two chiral carbons?
(A) L-Leucine
(B) L-Threonine
(C) L-Isoleucine
(D) L-Asparagine
Which Amino Acids Have Two Chiral Carbons? L-Leucine, L-Threonine, L-Isoleucine, or L-Asparagine
Amino acids with two chiral carbons are rare among the standard 20, as most feature just one at the alpha position. L-Threonine and L-Isoleucine stand out due to their unique side chains.
Correct Answer
L-Threonine (B) and L-Isoleucine (C) both contain two chiral carbons, making them the right choices for this multiple-choice query.
Amino Acid Structures
Standard L-amino acids have chirality at the alpha carbon, bonded to H, COOH, NH2, and R. Two chiral carbons require an additional asymmetric carbon in the side chain with four distinct groups.
Option Breakdown
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L-Leucine (A): Features an isobutyl side chain (-CH2-CH(CH3)2). The beta carbon attaches to two identical methyl groups, so no second chiral center exists.
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L-Threonine (B): Side chain is -CH(OH)-CH3. Both alpha and beta carbons qualify as chiral, as the beta bonds to H, OH, CH3, and the alpha chain.
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L-Isoleucine (C): Side chain -CH(CH3)-CH2-CH3 creates two chiral carbons: alpha and the beta with H, CH3, C2H5, and alpha linkage.
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L-Asparagine (D): Side chain -CH2-CONH2 has a beta carbon bound to two hydrogens, preventing chirality.
| Amino Acid | Chiral Carbons | Side Chain Structure |
|---|---|---|
| L-Leucine | 1 | -CH2-CH(CH3)2 |
| L-Threonine | 2 | -CH(OH)-CH3 |
| L-Isoleucine | 2 | -CH(CH3)-CH2CH3 |
| L-Asparagine | 1 | -CH2-CONH2 |
Related Searches: threonine chiral centers, isoleucine stereochemistry, leucine structure chirality, asparagine amino acid chiral carbons
