Question

1. which carbon skeleton represents a ketone? c - c - c - c - o c - c - c - c c - c - c - c = o c - c - c - c - o

Explanation:

A ketone has the general formula \( R - CO - R' \), where \( R \) and \( R' \) are alkyl or aryl groups. The carbonyl group (\( C = O \)) is in the middle of the carbon chain.

• The first option \( C - C - C - C - O \) is an alcohol (ends with \( - OH \) group, here the last \( O \) is likely part of \( - OH \) if we consider common organic structures).
• The second option \(

$$\begin{matrix}& & O \\ & & || \\ C - C - C - C\end{matrix}$$

\) has the carbonyl (\( C = O \)) group in the middle of the carbon chain, which is characteristic of a ketone.

• The third option \( C - C - C - C = O \) is an aldehyde (carbonyl group at the end of the chain, formula \( R - CHO \)).
• The fourth option \(

$$\begin{matrix}& & O \\ & & || \\ C - C - C - C - O\end{matrix}$$

\) has an extra \( O \) at the end, likely a combination of a ketone - like carbonyl and an alcohol - like \( - O \) group (not a simple ketone).

Answer:

The second option (the structure with \(

$$\begin{matrix}& & O \\ & & || \\ C - C - C - C\end{matrix}$$

\)) represents a ketone.