[darkprince304]

Hello.
I have a question.
Why does water have a bond angle of 105 degree but alcohols (say ethanol) have a bond angle of 109 degree.
I know oxygen in both compounds have lone pair.
Can someone explain it to me?

[fledarmus]

What do you know about the relative sizes of a methyl group and a hydrogen atom?

What would you expect if both hydrogen atoms were replaced by methyl groups - say, dimethyl ether?

[darkprince304]

I think it's something about the dipole moment?
Like Hydrogen atom has very less Dipole Moment and Alkyl groups have more so maybe the net effect of the dipole moment results in the 109 degree bond angle

I have read that the bond angle in water is due to the lone pair-lone pair repulsion of the lone pairs in oxygen atom which makes the angle small.
Why doesn't this affect the alkyl groups?

[fledarmus]

You are confusing cause and effect - dipole moment is an effect of the bond angle, not a cause of it.

You still haven't answered my question about the relative sizes of a hydrogen group and a methyl group...

[camptzak]

i know its a positive thing to make people think about questions instead of just answering them...
hydrogen is small in comparison to carbon, and this might effect the angle of seperation...