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What are the structural isomers of C8H18?

Craig Eckhoff  Follow

I don’t know of any algorithm that can calculate the number of structural isomers, given a molecular formula. So the only other way to approach this kind of question is to try to be systematic, lest you miss something.

What I did is draw backbones, first eight carbons (obviously only one isomer of n-octane), then seven carbons (and placed the methyl group in all chemically distinct positions), then six carbons (and placed either two methyls or one ethyl in all chemically distinct combinations of positions) … etc.

The numbers in the boxes are the length of the longest chain (the parent alkane) in each set.

Total isomers: 18.

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David Cousens  Follow
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