Octyl ethanoate

The first part of an ester name comes from the alkyl part of octanol, which would be octyl. The second part is obtained from the name of the carboxylic acid by replacing ic acid with ate. The name of the ester for orange flavor is octyl ethanoate. 

The odors of esters are distinctly different from those of the corresponding acids. Acids have unpleasant smells, but esters have fruity smells. In fact, esters are responsible for the odors of many fruits. For example, ethyl ethanoate occurs in pineapples, 3-methylbutyl ethanoate in apples and bananas, 3-methylbutyl-3-methylbutanoate in apples, and octyl ethanoate in oranges. 

The systematic name for an ester is formed by changing the -oic ending of the parent acid to -oate. The parent alcohol chain is named first with a -yl ending. For example, the systematic name for n-octyl acetate is -octylethanoate (from ethanoic acid). 

---