Chapter 16, Problem 31PP

 (a)

Interpretation Introduction

Interpretation: For the given molecular formulae the structure should be predicted.

Concept Introduction:

¹H NMR: A technique gives information to predict the Carbon and Hydrogen connectivity in the organic compounds.

HDI (Index of hydrogen deficiency): HDI values gives information on the level of unsaturation (means a double bond or a ring) on the structure of the compound.

$\begin{array}{l}\text{ HDI}\text{=}\frac{\left(\text{ 2C+2+N-H-X}\right)}{\text{2}}\\ \text{Where}\\ \text{Number}\text{of}\text{carbon}\text{atoms}\text{is}\text{C}\\ \text{Number}\text{of}\text{nitrogen}\text{atoms}\text{is}\text{N}\\ \text{Number}\text{of}\text{hydrogen}\text{atoms}\text{is}\text{H}\\ \text{Number}\text{of}\text{halogen}\text{atoms}\text{is}\text{X}\end{array}$

Answer to Problem 31PP

Answer

Explanation of Solution

To predict: the structure for the given molecular formula. ${\text{C}}_{\text{5}}{\text{H}}_{\text{10}}$

Calculate HDI Value for the given molecular formula and draw the structure.

$\begin{array}{l}{\text{C}}_{\text{5}}{\text{H}}_{\text{10}}:\\ \text{HDI}=\frac{2(5)+2-10}{2}\\ =\frac{2}{2}\\ =1\end{array}$

HDI = 1, compound has either 1 ring or one $\text{π}$-bond. If it is the unsaturated compound, it will give more than one signal thus it is wrong. In the saturated ring, all the protons are chemically equivalent through either axis of symmetry or plane of symmetry gives only one signal in the spectrum.

Therefore, the compound predicted is the cyclopentane.

(b)

Interpretation Introduction

Interpretation: For the given molecular formulae the structure should be predicted.

Concept Introduction:

¹H NMR: A technique gives information to predict the Carbon and Hydrogen connectivity in the organic compounds.

HDI (Index of hydrogen deficiency): HDI values gives information on the level of unsaturation (means a double bond or a ring) on the structure of the compound.

$\begin{array}{l}\text{ HDI}\text{=}\frac{\left(\text{ 2C+2+N-H-X}\right)}{\text{2}}\\ \text{Where}\\ \text{Number}\text{of}\text{carbon}\text{atoms}\text{is}\text{C}\\ \text{Number}\text{of}\text{nitrogen}\text{atoms}\text{is}\text{N}\\ \text{Number}\text{of}\text{hydrogen}\text{atoms}\text{is}\text{H}\\ \text{Number}\text{of}\text{halogen}\text{atoms}\text{is}\text{X}\end{array}$

Answer to Problem 31PP

Answer

Explanation of Solution

The structure of given molecular formula.( ${\text{C}}_5{\text{H}}_8{\text{Cl}}_4$)

Calculate HDI value for the given molecular formula and draw the structure:

$\begin{array}{l}{\text{C}}_5{\text{H}}_8{\text{Cl}}_4:\\ \text{HDI}=\frac{2(5)+2-8-4}{2}\\ =0\\ \end{array}$

HDI = 0 , tells the compound is fully saturated (no double bond, triple bond or rings) and the compound is acyclic. Only one proton signal indicates all 4- ${\text{ CH}}_{\text{2}}$ protons bonded to the same carbon possess high degree of symmetry.

Therefore the predicted compound is 1, 3-dichoro-2, 2-dimethylchloropropane.

 (c)

Interpretation Introduction

Interpretation: For the given molecular formulae the structure should be predicted.

Concept Introduction:

¹H NMR: A technique gives information to predict the Carbon and Hydrogen connectivity in the organic compounds.

HDI (Index of hydrogen deficiency): HDI values gives information on the level of unsaturation (means a double bond or a ring) on the structure of the compound.

$\begin{array}{l}\text{ HDI}\text{=}\frac{\left(\text{ 2C+2+N-H-X}\right)}{\text{2}}\\ \text{Where}\\ \text{Number}\text{of}\text{carbon}\text{atoms}\text{is}\text{C}\\ \text{Number}\text{of}\text{nitrogen}\text{atoms}\text{is}\text{N}\\ \text{Number}\text{of}\text{hydrogen}\text{atoms}\text{is}\text{H}\\ \text{Number}\text{of}\text{halogen}\text{atoms}\text{is}\text{X}\end{array}$

Answer to Problem 31PP

Answer

Explanation of Solution

To find:  the structure of given molecular formula. ${\text{C}}_{12}{\text{H}}_{18}$

Calculate HDI value for the given molecular formula and draw the  structure:

$\begin{array}{l}{\text{C}}_{12}{\text{H}}_{18}:\\ \text{HDI}=\frac{2(12)+2-18}{2}\\ =\frac{8}{2}\\ =4\\ \end{array}$

HDI = 4, shows the compound is aromatic ring (having 3 double bonds and 1 ring) having each methyl group (- ${\text{CH}}_{\text{3}}$ group) attached to carbon of the aromatic ring. All the eighteen protons are chemically equivalent through either axis of symmetry or plane of symmetry possessing high degree of symmetry.