Question

A student who stresses too much about his grades has incorrectly named an organic compound 3-propylhexane.

Answer 1

Answer:

None of these.

The correct answer should be, 4-ethylheptane.

Explanation:

In naming Alkanes, the general rules apply:

I. Identify the longest continuous carbon chain and name it as the root or parent name.

II. Identify any side chains and add their names and positions as a prefix to the parent chain.

III. When there are more than one type of side chain, name them alphabetically.

IV. Use hyphens between numbers and letters and commas between numbers.

V. Number your side chains to obtain the lowest number combinations possible.

For the above question,

first, attempt drawing only the carbon skeleton, of 3-propylhexane thus,

C-C-C-C-C-C

|

C-C-C

The longest continuous carbon chain (numbering from the top right) is 7 carbon atoms, hence, parent or root name is heptane. The 2 carbon atoms (at top left) not numbered make up the alkyl group called ethyl and since they are attached to carbon number 4 of the numbered carbon atoms ( whether the numbering is from top right to bottom right or vice versa ), their position and name should be written as a prefix to the parent name. That is why the organic compound is named, 4-ethylheptane.

Please note that in drawing the carbon skeleton of 3-propylhexane, the name is the same even if you start placing the bottom 3 carbon atoms on the 3rd carbon (top) from the left or from the right because the numbering can start from any side to achieve the lowest number combinations of numbering common Alkanes.