Chapter 13, Problem 13.103QP

Interpretation Introduction

Interpretation: The graph of carbon-to-hydrogen in aldehydes for the increasing number of carbon is to be plotted and compared with that of alkane and alkene.

Concept introduction: The general formula for the aldehydes is ${\text{C}}_{\text{2}}{\text{H}}_{\text{2n}}\text{O}$.

The general formula for the alkene is ${\text{C}}_{\text{2}}{\text{H}}_{\text{2n}}$

The general formula for the alkane is ${\text{C}}_{\text{2}}{\text{H}}_{\text{2n+2}}$

To determine: The plot of carbon-to hydrogen ratio and its comparison with that of alkane and alkene.

Answer to Problem 13.103QP

The plot of carbon to hydrogen ratio in aldehydes correlates better with the plot of carbon to hydrogen in alkenes.

Explanation of Solution

The molecular formula of aldehydes containing one to six carbons, the number of carbon and hydrogen atoms and its ratio is,

$\begin{array}{cccc}\begin{array}{l}\text{Molecular}\\ \text{formula}\end{array}& \begin{array}{l}\text{Number}\text{of}\\ \text{carbon}\text{atom}\end{array}& \begin{array}{l}\text{Number}\text{of}\\ \text{hydrogen}\text{atoms}\end{array}& \begin{array}{l}\text{Carbon}\text{to}\\ \text{hydrogen}\text{ratio}\end{array}\\ {\text{C}}_{\text{1}}{\text{H}}_{\text{2}}\text{O}& 1& 2& 1:2\\ {\text{C}}_{\text{2}}{\text{H}}_{\text{4}}\text{O}& 2& 4& 1:2\\ {\text{C}}_{\text{3}}{\text{H}}_{\text{6}}\text{O}& 3& 6& 1:2\\ {\text{C}}_{\text{4}}{\text{H}}_{\text{8}}\text{O}& 4& 8& 1:2\\ {\text{C}}_{\text{5}}{\text{H}}_{\text{10}}\text{O}& 5& 10& 1:2\\ {\text{C}}_{\text{6}}{\text{H}}_{\text{12}}\text{O}& 6& 12& 1:2\end{array}$

Table 1

From the above data it is concluded that the general formula for the aldehydes is ${\text{C}}_{\text{2}}{\text{H}}_{\text{2n}}\text{O}$ and the carbon to hydrogen ratio in aldehydes is $1:2$.

The plot of carbon-to-hydrogen ratio in aldehydes as a function of number of carbon atoms is,

Figure 1

The general formula for the alkene is ${\text{C}}_{\text{2}}{\text{H}}_{\text{2n}}$

The molecular formula of alkene containing one to six carbons, the number of carbon and hydrogen atoms and its ratio is,

$\begin{array}{cccc}\begin{array}{l}\text{Molecular}\\ \text{formula}\end{array}& \begin{array}{l}\text{Number}\text{of}\\ \text{carbon}\text{atom}\end{array}& \begin{array}{l}\text{Number}\text{of}\\ \text{hydrogen}\text{atoms}\end{array}& \begin{array}{l}\text{Carbon}\text{to}\\ \text{hydrogen}\text{ratio}\end{array}\\ {\text{C}}_{\text{1}}{\text{H}}_{\text{2}}& 1& 2& 1:2\\ {\text{C}}_{\text{2}}{\text{H}}_{\text{4}}& 2& 4& 1:2\\ {\text{C}}_{\text{3}}{\text{H}}_{\text{6}}& 3& 6& 1:2\\ {\text{C}}_{\text{4}}{\text{H}}_{\text{8}}& 4& 8& 1:2\\ {\text{C}}_{\text{5}}{\text{H}}_{\text{10}}& 5& 10& 1:2\\ {\text{C}}_{\text{6}}{\text{H}}_{\text{12}}& 6& 12& 1:2\end{array}$

Table 2

From the above data it is concluded that the carbon to hydrogen ratio in alkene is $1:2$.

The general formula for the alkane is ${\text{C}}_{\text{2}}{\text{H}}_{\text{2n+2}}$

The molecular formula of alkane containing one to six carbons, the number of carbon and hydrogen atoms and its ratio is,

$\begin{array}{cccc}\begin{array}{l}\text{Molecular}\\ \text{formula}\end{array}& \begin{array}{l}\text{Number}\text{of}\\ \text{carbon}\text{atom}\end{array}& \begin{array}{l}\text{Number}\text{of}\\ \text{hydrogen}\text{atoms}\end{array}& \begin{array}{l}\text{Carbon}\text{to}\\ \text{hydrogen}\text{ratio}\end{array}\\ {\text{C}}_{\text{1}}{\text{H}}_4& 1& 4& 1:4\\ {\text{C}}_{\text{2}}{\text{H}}_6& 2& 6& 1:3\\ {\text{C}}_{\text{3}}{\text{H}}_8& 3& 8& 3:8\\ {\text{C}}_{\text{4}}{\text{H}}_{10}& 4& 10& 2:5\\ {\text{C}}_{\text{5}}{\text{H}}_{\text{12}}& 5& 12& 5:12\\ {\text{C}}_{\text{6}}{\text{H}}_{\text{14}}& 6& 14& 3:7\end{array}$

Table 2

From the above data it is concluded that the carbon to hydrogen ratio in alkane changes as the numbers of carbon and hydrogen atom increases.

Therefore, the plot of carbon to hydrogen ratio in aldehydes correlates better with the plot of carbon to hydrogen in alkenes.

Conclusion

The plot of carbon to hydrogen ratio in aldehydes correlates better with the plot of carbon to hydrogen in alkenes.