Uploaded May 2020 | Updated September 2026, 2 weeks ago

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What Are Structural Isomers?

Different forms of the same molecule are known as structural isomers; they have the same molecular formula but are different 'shapes'.

In this video we will look at some different structures of butane - so they all have 4 carbons but just arranged differently.

We will also look at the the 5 different isomers for hexane - they all have 6 carbons (and hence are hexane isomers) but the longest chain length of carbons gives the isomer it's name. So if the longest chain is 5 carbons, it is a pentane and if the longest chain is 4 carbons it is a butane.
Hexane
2 - methylpentane
3 - methylpentane
2, 3-dimethylbutane
2,2-dimethylbutane

See the pentane and butane tells you the longest chain of carbons.

3-methyl tells us that the methyl group is on the 3rd carbon.

Structural isomers have the same molecular formula but different structural arrangements. And that the naming is based upon the length of the longest carbon chain, and where groups come off of these carbons.

CREDITS
Animation & Design: Cecil Juan Bouwer
Narration: Keith Ross

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