3
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Is the number of hyperconjugation structures for a hydrocarbon with number of 'alpha' hydrogens 'a' equal to 'a' or 'a+1'?

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3
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Let's use the n-propyl carbocation as an example. It has two hydrogens alpha to the cationic carbon and two resonance structures involving hyperconjugation of those alpha hydrogens can be drawn.

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    $\begingroup$ So total number of structures are 3 or 2 as itself is also a structure? $\endgroup$ – Aryaman Bansal Jun 22 '14 at 15:36
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    $\begingroup$ Total number of resonance structures is 3 $\endgroup$ – ron Jun 22 '14 at 15:39
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    $\begingroup$ What about the analogous structure using the C-methyl bond instead of the C-H bond? $\endgroup$ – jerepierre Jun 23 '14 at 18:41
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    $\begingroup$ Yes, resonance structures incolving C-C hyperconjugation are also valid resonance structures. In this case, C-C hyperconjugation probably contributes less to the overall picture of the molecule than C-H hyperconjugation. I didn't include such structures since the OP was asking about the alpha-hydrogens. $\endgroup$ – ron Jun 23 '14 at 18:54

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