6.2.2 - Amino acids, Amines and Chirality

Question 1

What are the two functional groups of amino acids?

Answer 1

NH2 and COOH (Amine and Carboxylic acid)

Question 2

Are a-amino acids chiral?

Why?

Answer 2

Yes
One carbon has 4 different substituents
Except glycine, where R=H

Question 3

Define a zwitterion

Answer 3

Ions which have both a permanent positive and negative charger, but are neutral overall

Question 4

How do zwitterions occur in amino acids?

Answer 4

COOH is deprotonated COO-

NH2 is protonated NH3+

Question 5

What happens to amino acids in acidic conditions?

Answer 5

Gains a proton on NH2 group

Question 6

What happens to amino acids in alkaline conditions?

Answer 6

Loses a proton from COOH group

forms COO-

Question 7

What is the peptide linkage?

Answer 7

-CONH-

Question 8

What are the structures of primary and secondary amides?

Answer 8

Primary amide = 1 carbon

Secondary amide = 2 carbons

Question 9

What property must a carbo atom have for the molecule to display optical isomerism about that carbon atom?

Answer 9

4 different substituents attached to one carbon atom

Question 10

What are the similarities and differences between two optical isomers?

Answer 10

Same atoms and bonds, but they are non-superimposable mirror images of one another.
NOT IDENTICAL in chemical properties necessarily

Differ in the way they rotate plan polarised light - rotate plan of polarisation by the same angle but in different directions

Question 11

What word is used to describe optically active molecules?

Answer 11

Chiral

Question 12

Give two examples of chiral molecules

Answer 12

All alpha amino acids, except glycine

Lactic acid / 2-hydroxypropanoic acid