[Fluorspar]

Hi all, new here

We've been doing some questions on the reactivity of compounds in regards to substitution and elimination reactions, and an issue that came up was over the effects of an ether. I had assumed that a methoxy group, for example, would be electron withdrawing (on a simple alkyl compound) because of the electronegative oxygen. However, various sources on the web are telling me otherwise. Are ether groups donating? If so, how strongly?

An example question is whether the reaction of NaN₃ in methanol would occur faster with CH₃OCH₂Cl or CH₃OCH₂CH₂Cl.

Thanks for the help

edit: Oh, the effects of an equivalent sulphide (CH₃OCH₂CH₂Cl vs CH₃SCH₂CH₂Cl) would be appreciated.

[souro10]

Whether a group is electron donatiing or electron withdrawing depends on a number of factors, and not just on inductive effect. In case a methoxy substituent is attached to an sp2 carbon (it can be a carbocation too, note that), the lone pairs on oxygen can move. Draw the resonating structures and convince yourself that due to resonance effect, methoxy group can act as electron donating. Now, usually for methoxy group it is found that resonance effect is much more pronounced than the inductive effect, and hence it can act as an electron donating group when there is a scope for the lone pairs on oxygen to 'move' . As for the comparison between SCH3 and OCH3, well, both oxygen and S belong to the same group on the periodic table(conclusion about electrons?) Which one is more electronegative? Use that fact. I do not think the compound CH3OCH2Cl that you posted is at all stable. Single bonded oxygen and halogen on a single carbon are often very unstable.

[willug]

Chloromethyl methyl ether is ok;

http://en.wikipedia.org/wiki/Chloromethyl_methyl_ether

Nasty stuff though. Highly carcinogenic. If you look up 'Neighbouring group participation';

http://en.wikipedia.org/wiki/Neighbouring_group_participation

that might give you some ideas about the NaN3 question.