Isn't this a deactivating group?

[FROGGBUSTER]

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Destroyer says it's not but i'm unsure why. Electrons can't donate into the benzene ring thru resonance and it seems like the groups is inductively withdrawing, so I'm clueless.

Can someone explain? Thanks.

edit: #54 in Destroyer.

I think I wasn't clear. That substituent should be connected to a benzene ring. I am assuming one of the 2 alkyl groups would be directly connected to the benzene ring, in which case I think it would be deactivating and a meta director.

 

[LaughingGas]

Destroyer says it's not but i'm unsure why. Electrons can't donate into the benzene ring thru resonance and it seems like the groups is inductively withdrawing, so I'm clueless.

Can someone explain? Thanks.

number of question and full structure would be helpful, at least to me.

 

[molar3]

isnt that the same thing as -OR which is a activating group. the weird connecetion part just being the -R

 

[NYMedKidd22]

Destroyer says it's not but i'm unsure why. Electrons can't donate into the benzene ring thru resonance and it seems like the groups is inductively withdrawing, so I'm clueless.

Can someone explain? Thanks.

Be careful, unless I'm mistaken because there's part of this molecule that is missing from your pic, it isn't a benzene ring. Its a cyclic ether.

The strongest donator is an N with lone pair of electrons.
The 2nd strongest donator is an O with lone pairs. Although they aren't drawn here, since there aren't any charge drawn (which they would) on the oxygens, it means they're happy and have a full octet. But since they're only making 2 bonds, it means they have 2 lone pairs each, hence they are the 2nd strongest donators!

Hope that helps bud 🙂

 

[FROGGBUSTER]

Sorry, it's #54 in Destroyer 2011.

Be careful, unless I'm mistaken because there's part of this molecule that is missing from your pic, it isn't a benzene ring. Its a cyclic ether.

The strongest donator is an N with lone pair of electrons.
The 2nd strongest donator is an O with lone pairs. Although they aren't drawn here, since there aren't any charge drawn (which they would) on the oxygens, it means they're happy and have a full octet. But since they're only making 2 bonds, it means they have 2 lone pairs each, hence they are the 2nd strongest donators!

Hope that helps bud 🙂

Hey, thanks for the response, but I think I wasn't clear. That substituent should be connected to a benzene ring. I am assuming one of the 2 alkyl groups would be directly connected to the benzene ring, in which case I think it would be deactivating and a meta director.

 

[LaughingGas]

My guess is that you have to see that as similar to alkyl groups as you mentioned. Alkyl groups are weakly activating, b/c theycan donate electrons by hyperconjugation. Although the Oxygen group are part of the structure, I'm guessing is too far away from the benzene ring, that hyperconjugation effect is stronger than inductive electron withdrawing effect.

 

[FROGGBUSTER]

My guess is that you have to see that as similar to alkyl groups as you mentioned. Alkyl groups are weakly activating, b/c theycan donate electrons by hyperconjugation. Although the Oxygen group are part of the structure, I'm guessing is too far away from the benzene ring, that hyperconjugation effect is stronger than inductive electron withdrawing effect.

you know, i'm actually unsure which structure Dr. Romano means.

I assumed it was the one on the left, but if it's the one on the right your explanation would work I think.

How did you understand the question when you read it? lol

 

[LaughingGas]

u hu... My bad, I was only visualizing the one on the right, since except for option C (to clarify you are attaching to a quarternary nitrogen), A,B doesnt show the dash line for bonding. Usually the dash line would represent an alkyl group so I imagined the structure on the right.....

Now you got me thinking hahahahha

 

[Troyvdg]

its an activating group, just like any other alkyl group would be, alkyl groups don't donate electrons through resonance, they donate electron density! think about it, if you remove a H (as you would in electrophilic aromatic substitution) that is ortho or para to this group, where would the positive charge move around the ring? try it and draw out the resonance structures, you'll find out that when an H is removed from the ortho or para position, one of the resonance structures has the positive charge on the TERTIARY CARBON that is attaching the acetal substituent you are questioning, which can donate electron density to stabilize the positive charge

hope this helped!

 

[FROGGBUSTER]

its an activating group, just like any other alkyl group would be, alkyl groups don't donate electrons through resonance, they donate electron density! think about it, if you remove a H (as you would in electrophilic aromatic substitution) that is ortho or para to this group, where would the positive charge move around the ring? try it and draw out the resonance structures, you'll find out that when an H is removed from the ortho or para position, one of the resonance structures has the positive charge on the TERTIARY CARBON that is attaching the acetal substituent you are questioning, which can donate electron density to stabilize the positive charge

hope this helped!

i'm aware that alkyl groups are inductively electron-donating. in the structure on the left, the O's are very electronegative so wouldn't they pull electrons away from the Carbon? the carbon wouldn't be able to donate its electrons because of the oxygens, or that is what i think.

 

[Troyvdg]

if you were to add acid, then yes, it would be a deactivating group because it would return to is ketone form, however, in its acetal form it is a weak activating group, for the same reason I mentioned above

 

[LetsGo2DSchool]

SDN is a deactivating group... from studying.

 

[FROGGBUSTER]

if you were to add acid, then yes, it would be a deactivating group because it would return to is ketone form, however, in its acetal form it is a weak activating group, for the same reason I mentioned above

i'm very sorry, i'm not sure i understand.

can you please explain why the presence of the Oxygens doesn't make the substituent electron-withdrawing?

 

[wylde923]

I like to think of it as almost all the deactivating groups have pi electrons (a double bond) one atom out from the ring. And oxygens don't always lead to electron withdrawal, as in the case with the electron donating carboxy substituent (-OR), because they have electrons to donate. But again, if those oxygens are part of a pi system (double bond) they will lead to that group being electron withdrawing (acyl groups, carboxy acid derivatives etc.)

Hope that helps

 

[FROGGBUSTER]

I like to think of it as almost all the deactivating groups have pi electrons (a double bond) one atom out from the ring. And oxygens don't always lead to electron withdrawal, as in the case with the electron donating carboxy substituent (-OR), because they have electrons to donate. But again, if those oxygens are part of a pi system (double bond) they will lead to that group being electron withdrawing (acyl groups, carboxy acid derivatives etc.)

Hope that helps

hey thanks for the response. i think i get the main principles of electron withdrawing/donating groups though, it's just this one example that is driving me crazy.

i posted the 2 possible structures that dr. romano could have meant in regards to his destroyer question. the one on the left i absolutely cannot see why it's electron-donating, and i think laughinggas was agreeing with me. but troy i think is saying that the 2 oxygens will not pull electrons away to a degree such that it affects the donating effect? i just find that hard to believe since there are 2 oxygens.

the one on the right on the other hand, i could see why it would be weakly activating.