The total number of C-C sigma bond/s in mesityl oxide ($$C_6H_{10}O$$) is ________ (Round off to the Nearest Integer).

Mesityl oxide is a well-known organic compound with the molecular formula $$\text{C}_6\text{H}_{10}\text{O}$$ and the IUPAC name 4-methylpent-3-en-2-one. Its structure is $$(\text{CH}_3)_2\text{C}=\text{CH}-\text{CO}-\text{CH}_3$$.

Let us write out the carbon skeleton and count all C-C sigma bonds. The structure has six carbon atoms arranged as: $$\text{CH}_3 - \text{C}(\text{CH}_3) = \text{CH} - \text{C}(=\text{O}) - \text{CH}_3$$.

The C-C sigma bonds are: (1) the first $$\text{CH}_3$$ to the central carbon $$\text{C}$$, (2) the branching $$\text{CH}_3$$ to the same central carbon, (3) the $$\text{C}=\text{C}$$ double bond contains one sigma and one pi bond, so there is one C-C sigma bond here, (4) between $$=\text{CH}$$ and the carbonyl carbon $$\text{C}(=\text{O})$$, and (5) between the carbonyl carbon and the terminal $$\text{CH}_3$$.

This gives a total of 5 C-C sigma bonds.

The answer is 5.