Ochem - Carbon stability

[sfoksn]

Advertisement - Members don't see this ad

Why is branched carbon chain more stable than the linear carbon chain?

 

[redchesus]

what do you mean by stability?

if you're talking about volatility (i.e. related to vapor pressure) I think it's the opposite, branching tends to reduce intermolecular forces which makes the molecule more likely to enter the gas phase (vaporize) and less stable

if you're talking about carbocation stability... that's different

 

[sfoksn]

I am talking about the heat of hydrogenation.

more stable carbon chain release less heat, they say.

and apparently branched carbons release less heat so I thought they were more stable somehow..

Any ideas?

 

[299678]

branching enhances symmetry, which in turn enhances the ability of the molecules to form crystal lattice.

 

[Bio Dental Mom]

Not only the above answers, but if you think about how carbon reacts... the more branched it is tertiary, secondary, etc.. the more it is able to form a more stable carbocation and can handle the added charge - the same idea applies to radicals as well.

 

[Cofo]

Actually, branching reduces the ability of the carbon chain to participate in intermolecular forces, and consequently, the branched carbon chain will not be as stable as a linear carbon chain.
The linear carbon chain has more surface area to allow for more intermolecular forces to exist between it and other carbon chains.

 

[TexasOMFS]

^This question is from destroyer right? They never mentioned why a branched alkane is more stable but I'd venture to guess that there are many stabilizing effects a branched alkane has that a straight-chain alkane has not. What some of the ppl are stating above (ie: intermolecular forces, lattice packing) has little to do with inherent stability of the molecule. These factors make a difference towards melting and boiling point, yes, but stability would be better defined as the tendency for a molecule to react. While you can make a case for electron donating ability, I'm sure bond connectivity and spatial arrangements of bonds play a role also, and perhaps even Newman projections. Whatever the answer may be, you don't need to know it because it's not something you learn at this level. Just remember that branched chain alkanes are less reactive (more stable) and you'll be good.

 

[sfoksn]

Thanks everyone for your input.

 

[redchesus]

I always thought heat of hydrogenation had to do with alkenes and alkynes anyway. I haven't seen too many hydrogenation reactions of alkanes to be honest at the GChem or OChem level.

 

[TexasOMFS]

I always thought heat of hydrogenation had to do with alkenes and alkynes anyway. I haven't seen too many hydrogenation reactions of alkanes to be honest at the GChem or OChem level.

I believe the OP meant heat of combustion, as this is what I remember the problem being about.