Chapter 20.8, Problem 16P

Interpretation Introduction

Interpretation:

Using ¹H and ¹³CNMR spectroscopy how to distinguish between the isomers cyclopentanecarboxylic acid and 4-hydroxycyclohexanone is to be shown.

Concept introduction:

In ¹HNMR, the acidic COOH proton normally absorbs as a singlet, broadened in few cases, near 12 δ. In ¹HNMR the aldehyde protons absorb near 10 δ with a coupling constant , J = 3Hz. Hydrogens on the carbon next to aldehyde group absorb near 2.0-2.3 δ. Methyl ketones show a sharp three proton singlet near 2.1 δ. In ¹³CNMR, the carboxyl carbon absorb in the range 165-185 δ. The aromatic and α, β -unsaturated acids absorb near 165 δ and saturated aliphatic acids near 185 δ. The nitrile carbons absorb in the range 115-130 δ. In ¹³CNMR, carbons in double bond which are sp² hybridized absorb from 110 to 220 δ. Saturated aldehydes and ketones usually absorb in the region from 200 to 215 δ While aromatic and unsaturated carbonyl compounds absorb in the 190 to 200 δ region.

To show:

Using ¹H and ¹³CNMR spectroscopy how to distinguish between the isomers cyclopentanecarboxylic acid and 4-hydroxycyclohexanone.