Chapter 21, Problem 26P

For each amino acid: [1] draw the L enantiomer in a Fischer projection; [2] classify the amino acid as neutral, acidic, or basic; [3) give the three-letter symbol; [4] give the one-letter symbol.

1. arginine
2. tyrosine
3. glutamic acid
4. valine

Interpretation Introduction

(a)

Interpretation:

The L-isomer of arginine in Fisher projection needs to be drawn and identified as acidic, basic or neutral. The three letter and one symbol for it needs to be determined.

Concept Introduction:

Like monosaccharides, the prefixes D and L are used to designate the arrangement of groups to the chiral center of amino acid, when drawn with a vertical carbon chain having $-{\text{COO}}^{-}$ group at the top and R group at the bottom.

Amino acids that have the ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection is called as L isomer. For example,

Answer to Problem 26P

• L isomer of arginine is as follows:

• In arginine, an additional basic nitrogen present. So, it is basic in nature.
• Three-letter symbol for arginine is 'Arg'.
• One letter symbol is 'R'.

Explanation of Solution

Amino acids that have the ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection is called as L isomer.

To draw the Fisher projection of arginine, place the $-{\text{COO}}^{-}$ group at the top and R group, that is,

at the bottom and to draw L isomer draw ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection. Hence, L isomer of arginine is as follows:

Here, R group is as follows:

In arginine, an additional basic nitrogen present. So, it is basic in nature.

Three-letter symbol for arginine is Arg and one letter symbol is R.

Interpretation Introduction

(b)

Interpretation:

The L-isomer of tyrosine in Fisher projection needs to be drawn and identified as acidic, basic or neutral. The three-letter and one symbol for it needs to be determined.

Concept Introduction:

Like monosaccharides, the prefixes D and L are used to designate the arrangement of groups to the chiral centre of amino acid, when drawn with a vertical carbon chain having $-{\text{COO}}^{-}$ group at the top and R group at the bottom.

Amino acids that have the ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection is called as L isomer. For example,

Answer to Problem 26P

• L-isomer of tyrosine is as follows:

• Tyrosine is neutral in nature.
• Three-letter symbol for tyrosine is 'Tyr'.
• One letter symbol for tyrosine is 'Y'.

Explanation of Solution

Amino acids that have the ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection is called as L isomer.

To draw the Fisher projection of tyrosine by placing the $-{\text{COO}}^{-}$ group at the top and R group, that is,

at the bottom and to draw L isomer draw ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection. Hence, L isomer of tyrosine is as follows:

The overall charge of tyrosine is zero as there is one positive and negative charge. Hence, tyrosine is neutral in nature.

Three-letter symbol for tyrosine is 'Tyr' and one letter symbol is 'Y'.

Interpretation Introduction

(c)

Interpretation:

The L-isomer of glutamic acid in Fisher projection needs to be drawn and identified as acidic, basic or neutral. The three-letter and one symbol for it needs to be determined.

Concept Introduction:

Like monosaccharides, the prefixes D and L are used to designate the arrangement of groups to the chiral centre of amino acid, when drawn with a vertical carbon chain having $-{\text{COO}}^{-}$ group at the top and R group at the bottom.

Amino acids that have the ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection is called as L isomer. For example,

Answer to Problem 26P

• L-isomer of glutamic acid is as follows:

• Glutamic acid is acidic in nature.
• Three-letter symbol for glutamic acid is 'Glu'.
• One letter symbol for glutamic acid is 'E'.

Explanation of Solution

Amino acids that have the ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection is called as L isomer.

Draw the Fisher projection of glutamic acid by placing the $-{\text{COO}}^{-}$ group at the top and R group, that is, ${\text{CH}}_{\text{2}}{\text{CH}}_2{\text{COO}}^{-}$ at the bottom and to draw L-isomer draw ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection. Hence, L-isomer of glutamic acid is as follows:

In glutamic acid, one additional acidic carboxyl group present. So, glutamic acid is acidic in nature.

Three-letter symbol for glutamic acid is 'Glu' and one letter symbol for glutamic acid is 'E'.

Interpretation Introduction

(d)

Interpretation:

The L-isomer of valine in Fisher projection needs to be drawn and identified as acidic, basic or neutral. The three-letter and one symbol for it needs to be determined.

Concept Introduction:

Like monosaccharides, the prefixes D and L are used to designate the arrangement of groups to the chiral centre of amino acid, when drawn with a vertical carbon chain having $-{\text{COO}}^{-}$ group at the top and R group at the bottom.

Amino acids that have the ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection is called as L isomer. For example,

Answer to Problem 26P

• L-isomer of valine is as follows:

• Valine is neutral in nature.
• Three-letter symbol for valine is 'Val'.
• One letter symbol for valine is 'V'.

Explanation of Solution

Amino acids that have the ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection is called as L isomer.

Draw the Fisher projection of valine by placing the $-{\text{COO}}^{-}$ group at the top and R group, that is,

  $\text{-C}{\left({\text{CH}}_{\text{3}}\right)}_2$ at the bottom and to draw L-isomer draw ${\text{-NH}}_{\text{3}}{}^{+}$ group on the left side of Fisher projection. Hence, L-isomer of valine is as follows:

The net charge in valine is zero as there is one positive charge and negative charge in the compound. So, valine is neutral.

Three-letter symbol for valine is 'Val' and one letter symbol for valine is 'V'.