Chapter 19, Problem 96CP

(a)

Interpretation Introduction

Interpretation:

The structure of the compound with the molecular formula ${\text{C}}_8{\text{H}}_{\text{14}}\text{O}$ which gives six signals in the ${}^{\text{1}}\text{H}$ NMR spectrum has to be identified.

Concept Introduction:

NMR spectroscopy:

It is the study of the interaction between electromagnetic radiation and the nuclei of atoms and the variety of nuclei studied includes ${}^{\text{1}}\text{H,}{}^{\text{13}}\text{C,}{}^{\text{15}}\text{N,}{}^{\text{19}}\text{F}\text{and}{}^{\text{31}}\text{P}$

Chemical shift: The frequency of the proton signal in the spectrum with reference to the standard compound  which may be TMS(Tetramethylsilane) shows signal at 0 ppm(parts per million).

Integration value (I): The integration value at the bottom of the ${}^{\text{1}}\text{H}\text{NMR}$ spectrum represents the number of protons giving rise to the signal.

Rule: Multiplicity of each signal is calculated using $\text{(n+1)}$ rule only when the neighboring protons are chemically equivalent to each other.

$\begin{array}{l}\text{(n+1)}\\ \text{where }\\ \text{n indicates number of neighboring protons}\end{array}$

FUNCTIONAL GROUP	EFFECT ON THE ALPHA PROTONS	EFFECT ON THE BETA PROTONS
Oxygen of an alcohol or ether	$\text{+2}\text{.5}$	$\text{+0}\text{.5}$
Oxygen of ester	$\text{+3}\text{.0}$	$\text{+0}\text{.6}$
Carbonyl groups	$\text{+1}\text{.0}$	$\text{+0}\text{.2}$

(b)

Interpretation Introduction

Interpretation:

A plausible mechanism for the formation of compound B has to be provided.

Concept Introduction:

Lithium aluminum hydride: Act as strong nucleophilic reducing agent, used to reduce the polar multiple bonds like carbonyl bonds. It can reduce aldehyde to primary alcohol, ketones to secondary alcohol, carboxylic acid and esters to primary alcohols, amides and nitriles to amines, epoxides to alcohols and lactones to diols.