EAS question

[Fariba]

I am hoping someone will clarify a few things for me:

1. Wouldn't -CH2X (halomethyl) on a benzene make it meta directing? My reasoning is that the more electronegative X would cause C to have a slight + charge? My book is listing it under O/P directing. Could someone explain?

2. I understand why NR1 and NR2 are O/P directors, but why wouldn't NR3 also be O/P directing? N is more electronegative than the carbons... so it would have a slight negative charge making it O/P. What is the 3rd R group doing to change it?

Thanks!

---

Members don't see this ad.

 

[dat_student]

I am hoping someone will clarify a few things for me:

1. Wouldn't -CH2X (halomethyl) on a benzene make it meta directing? My reasoning is that the more electronegative X would cause C to have a slight + charge? My book is listing it under O/P directing. Could someone explain?

halomethyls are o-, p-directing & deactivating because of the halogen part....

2. I understand why NR1 and NR2 are O/P directors, but why wouldn't NR3 also be O/P directing? N is more electronegative than the carbons... so it would have a slight negative charge making it O/P. What is the 3rd R group doing to change it?

Thanks!

In -NR3, N is positively charged & doesn't have a lone pair of electrons.

 

[Fariba]

I completely understand the NR3 part. I dont know why I didnt see that. But I still do not understand why the halogen makes it o/p? I understand why a halogen DIRECTLY attached to the benzene is o/p deactivating... but wouldnt the halogen NEXT TO the carbon attached to the benzene pull carbon's electrons away, so that carbon gets a slight positive charge?

Thanks for the quick response, by the way!

 

[tom_servo_dds]

I completely understand the NR3 part. I dont know why I didnt see that. But I still do not understand why the halogen makes it o/p? I understand why a halogen DIRECTLY attached to the benzene is o/p deactivating... but wouldnt the halogen NEXT TO the carbon attached to the benzene pull carbon's electrons away, so that carbon gets a slight positive charge?

Thanks for the quick response, by the way!

In my O-Chem textbook it has -CH2X as being even more deactivating (but still O-P directing) than a straight -X would.

 

[Fariba]

In my O-Chem textbook it has -CH2X as being even more deactivating (but still O-P directing) than a straight -X would.

I am just having a mental block on this. I cannot understand how the C in -CH2X would not have a slight positive charge to it.

Oh well! I guess I really shouldn't worry about it because A)I don't think I will EVER forget that it is o-p directing and B) I have probably annoyed a few of you with my cluelessness.

Thanks for your patience!