Why does a primary alcohol show more hydrogen bonding

[Meredith92]

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In the Berkeley review answer key it says because there is less steric hindrance but I thought it had more to do with inductive electron donating properties. Wouldn't a more highly substituted alcohol ( substituted w more alkyl groups) have more electrons donation and therefore the hydrogen will be less electro positive and therefore have less h bonds?

Which is the better way to think about it? I may be getting this confused with properties involving acids ...

 

[Shjanzey]

.;

 

[BerkReviewTeach]

In the Berkeley review answer key it says because there is less steric hindrance but I thought it had more to do with inductive electron donating properties. Wouldn't a more highly substituted alcohol ( substituted w more alkyl groups) have more electrons donation and therefore the hydrogen will be less electro positive and therefore have less h bonds?

Which is the better way to think about it? I may be getting this confused with properties involving acids ...

You're absolutely right about the alkyl groups donating electron density, but that impacts more than just the partial positive on the H. It also impacts the partial negative on the O. An H-bond requires an electron-rich atom such as O to donate electron density to and electron-poor H like the one on the alchohol. The alkyl donation effect on O makes it a better donor and therefore better at forming H-bonds. The alkyl donation effect on H makes it a worse acceptor and therefore worse at forming H-bonds. The two effects nearly offset one another, so the impact of alkyl donation becomes less significant than steric hindrance.

 

[Meredith92]

Ah great answer! I forgot to think about the effect on the electron donor ( oxygen ) thanks for the help!

 

[BerkReviewTeach]

Isn't it an oddly nice feeling when you realize that a tiny piece of information clears something up?

 

[Meredith92]

It's an awesome feeling! The questions in tbr are actually great for doing that. It makes studying much more enjoyable. I probably sound like a tbr rep right now but I promise I'm not haha