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What is the difference between an identical and a structural isomer?

Answer 1

#"Structural isomers"# have identical chemical formulae, but different connectivity.

The given definition is best illustrated by an example: consider the isomers possible for #"butane"#, whose formula is #C_4H_10#.

Two structual isomers are possible: #"n-butane"#, #H_3C-CH_2CH_2CH_3#, and so-called #"isobutane"#, #H_3C-CH(CH_3)CH_3#. Clearly, these have the the same chemical formula, #C_4H_10#, but they have different connectivity, which results in different physical properties, viz. boiling point, #-0.5# #""^@C#, #"n-butane"#, versus #-11.7# #""^@C#, #"isobutane"#.

As expected the longer hydrocarbyl chain of #"n-butane"# allows for greater #"van der Waals"# interaction between the chains, and an increased boiling point with respect to #"isobutane"#.

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Answer 2

Madison Anderson

Identical isomers have the same molecular formula and the same structural formula. Structural isomers have the same molecular formula but different structural formulas.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.