Chapter 12, Problem 12B.9P

(a)

Interpretation Introduction

Interpretation:

The reason as to why the ${}^1\text{H}$ NMR spectrum of cyclohexane shows a single peak at room temperature but shows two peaks when the temperature is lowered is to be stated.

Concept introduction:

Many nuclei and electrons have spin, due to this spin magnetic moment arises.  The energy of this magnetic moment depends on the orientation of the applied magnetic field.  In NMR spectroscopy, every nucleus has a spin.  There is an angular momentum related to the spin.  The difference between its resonance frequency and that of the reference standard is known as the chemical shift of a nucleus.  Tetramethylsilane (TMS) is taken as reference.

(b)

Interpretation Introduction

Interpretation:

The reason as to why the ${}^{19}\text{F}$ NMR spectrum of ${\text{PF}}_{\text{5}}$ shows two lines even at the lowest experimentally accessible temperature has to be stated.

Concept introduction:

Same as metioned in concept introduction in part (a).

(c)

Interpretation Introduction

Interpretation:

The reason as to why the triplet and quartet obtained in the ${}^1\text{H}$ NMR spectrum of ethanol shows additional splitting if water is excluded from the sample has to be stated.

Concept introduction:

Same as metioned in concept introduction in part (a).