The Eight C6H12O2 Carboxylic Acids

Acid
# 13C Signals
# Unique Methyls
Area of Methyls
1H Multiplicity
1
6
1
3
t
2
6
2
3, 3
t, d
3
6
2
3, 3
t, d
4
6*
3
3, 3, 3
d, d, d
5
5#
1
6
d
6
5#
2
3, 6
t, s
7
4#
1
6
t
8
4&
1
9
s

*The methyls (blue arrows) are diastereotopic.

# The methyls (red arrows) are enantiotopic.

& The methyls (green arrows) are homotopic.

For a review of topicity, go here.