Chapter 13.12, Problem 20P

Interpretation Introduction

Interpretation:

The structure of an alcohol of given molecular formula C₄H₁₀O to be predicted using ¹³CNMR spectra.

Concept introduction:

The ¹³CNMR spectrum gives information on the different electronic environments of carbon. As like ¹HNMR, the number of signals generated in ¹³CNMR are predicted by performing symmetry operations (rotation or reflection symmetry). Only chemical shift values are reported in the spectrum but not the multiplicity and integration values because the coupling between two neighboring ¹³C-¹³ C nuclei are weakly involved due to the low abundance of ¹³C isotopes of carbon atom.

To Identify:

The structure of an alcohol of given molecular formula C₈H₁₆O.

Broadband-decoupled ¹³CNMR spectrum:

The spectra provide information regarding the total number of carbon environments.

DEPT (Distortionless enhancement by polarization transfer):

a) DEPT-90: The spectrum exhibits signal only from CH group and no signals from CH₃, CH₂, CH and quaternary carbon (carbon with no protons).

b) DEPT-135: The spectrum exhibits CH₃ groups and CH groups as positive signals (pointing up); CH₂ groups appear as negative signals (pointing down) and quaternary carbon does not appear.

The signals appear in each type of spectrum: