Question

What is the value of n in CH3(CH2)nCH3 if the name of the hydrocarbon is heptane

Answer 1

Answer:

n+5 so the correct answer is b) 5

Explanation:

just did review on edge

Answer 2

Answer:

n = 5.

Explanation:

How many carbon atoms in total in this straight-chain hydrocarbon?

The prefix of the IUPAC name of a hydrocarbon (the part before -ane) shows the number of carbon atoms on the longest carbon chain.

$\begin{array}{c|c}\text{Number of Carbon}\\ \text{atoms in backbone} & \text{Prefix}\\[-0.5em]\multicolumn{2}{c}{\rule{5cm}{0.5pt}}\\1& \text{meth-} \\ 2&\text{eth-} \\ 3&\text{prop-}\\4 & \text{but-}\\5 & \text{pent-} \\ 6 & \text{hex-} \\ 7 & \text{hept-} \\8 & \text{oct-}\\ \dots & \dots\end{array}$.

• Name of this hydrocarbon: heptane;
• Prefix: hept-;
• Number of carbon atoms in the longest chain: 7.

Hence the structure:

$\text{CH}_3\text{-CH}_2\text{-CH}_2\text{-CH}_2\text{-CH}_2\text{-CH}_2\text{-CH}_3$.

All the $\text{-CH}_2\text{-}$ in the formula might look redundant. "$\text{CH}_2$" appears five times in a row and may be condensed into $(\text{CH}_2)_5$. Hence the condensed formula:

$\text{CH}_3\text{-}{(\text{CH}_2)_{\bf5}\text{-CH}_3$.

Therefore $n = 5$.