Chapter 14, Problem 1Q

Interpretation Introduction

Interpretation:

The infrared spectra for carvone and limonene needs to be interpreted. Also, the proton and carbon-13 NMR spectra of carvone needs to be explained.

Concept Introduction:

In the IR spectroscopy, the IR region of the electromagnetic spectrum is studied. Here, light has a longer wavelength than the visible light. In this, the interaction of molecules with the IR light is studied.

Nuclear Magnetic Resonance (NMR) spectroscopy is a logical chemistry method used in quality control.

It studies for defining the material and purity of a sample and their molecular structure. It explains magnetic energy levels undergoing the resonance transition when the atomic nuclei are exposed to an external magnetic field and an electromagnetic radiation is applied with the specific frequency. The NMR spectrum is obtained by detecting the absorption signals.

Explanation of Solution

The structure of limonene is represented as follows:

  

Limonene will have C-H stretching at 3000 cm-1 and C=C stretching at 1645 cm-1

Now, the structure of Carvone is represented as follows:

  

Carvone will have C=C stretching at 1645 cm-1 and a, β-unsaturated ketone will have stretching at 1672 cm-1.

The structures of Carvone are given below along with the NMR interpretation (both ¹H and ¹³C).

  

Carvone NMR (¹H and ¹³C)

In the NMR of Carvone two methyl peaks are there along with vinylic protons. There are few CH₂ protons. In 13-C there are a, β-unsaturated ketone peak along with C=C peaks. Two methyl peaks and CH₂ peaks.

In NMR of limonene there are two methyl peaks, few CH₂ peaks and vinylic protons. In 13-C there are two methyl along with C=C and CH₂ peaks.