BR O-chem basic sites on molecule

[Jay2910]

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Hello everyone,

I have a question on #25 on the BR-O chem( its from passage IV). The question asks
What is the most basic site on the following molecule?

1) Can someone give me an alternate explanation as to why c would be the choice?
2) I assumed that the "R" can be any group, and so for simpleness sake, I just thought of it as another H, I also knew that Nitrogens were a little more basic in general compared to oxygens.
3) So, why isn't D the answer? There was a discrete similar to this( Example 1.19). In that explanation, they said that Nitrogen C would be the most basic cause its not being shared with anything else as much as the others. Why doesn't this same logic apply to this program?

Thanks in advance. I would greatly greatly appreciate your help!

 

[Ssina]

I don't have the book in front of me, but I think I know which question you are talking about

Here you need to find the nitrogen with the most available lone pair that is able to donate (hence most basic)... the lone pair on all other Nitrogens, besides C, are involved in resonance so they are less available.... at C, the Nitrogen is already double boned to the neighboring atom, so it's lone pair are not involved in resonance structures.

Sent from my SGH-T959 using Tapatalk

 

[Jay2910]

I don't have the book in front of me, but I think I know which question you are talking about

Here you need to find the nitrogen with the most available lone pair that is able to donate (hence most basic)... the lone pair on all other Nitrogens, besides C, are involved in resonance so they are less available.... at C, the Nitrogen is already double boned to the neighboring atom, so it's lone pair are not involved in resonance structures.

Sent from my SGH-T959 using Tapatalk

yes, that part I understood really well. But I don't know how to apply that same logic to question 25 on Passage IV. Perhaps I should upload the photo in another post if I can.

 

[Jay2910]

yes, that part I understood really well. But I don't know how to apply that same logic to question 25 on Passage IV. Perhaps I should upload the photo in another post if I can.

This is the link to my problem. It has the picture of the molecule.

http://i1072.photobucket.com/albums/w371/Goldeolde/IMAG0116.jpg

 

[GeauxTime]

yes, that part I understood really well. But I don't know how to apply that same logic to question 25 on Passage IV. Perhaps I should upload the photo in another post if I can.

My logic: Carbonyl Oxygens (O's) are almost always going to be most basic. Both 'a' and 'd' donate electrons to resonate with the carbonyl group, but the carbonyl O on the left side is only 50% (since it has the same electronegativity as the O right next to it) while the carbonyl O on the right side is more electronegative than the N (more than 50% negative). This means that 'c' will have a greater negative partial charge than 'd', making it more basic.

Possibly?

 

[Ssina]

I guess I didn't know which question you were referring to after all! (thanks for the pic)

well I wouldn't pick A or D because of what you already mentioned (when referring to the other example) that both lone pairs are being shared and there isn't really a lone paire on Nitrogen at D (just like in a peptide bond which is planar and can't rotate easily) so A and D would have a partial positive due to resonance... so for me it comes down to C or B!

And (again as you mentioned) Nitrogen being less electronegative is more basic and more willing to donate the lone paire so the oxygen would have a little bit more electron density at C vs. B.

 

[MedPR]

Hello everyone,

I have a question on #25 on the BR-O chem( its from passage IV). The question asks
What is the most basic site on the following molecule?

1) Can someone give me an alternate explanation as to why c would be the choice?
2) I assumed that the "R" can be any group, and so for simpleness sake, I just thought of it as another H, I also knew that Nitrogens were a little more basic in general compared to oxygens.
3) So, why isn't D the answer? There was a discrete similar to this( Example 1.19). In that explanation, they said that Nitrogen C would be the most basic cause its not being shared with anything else as much as the others. Why doesn't this same logic apply to this program?

Thanks in advance. I would greatly greatly appreciate your help!

Pretty sure R in organic chemistry are alkyl groups only.

 

[GeauxTime]

Pretty sure R in organic chemistry are alkyl groups only.

EDIT: Yes...

R = (CH2)n(CH3)

 

[Jay2910]

Thank you everyone for helping answer my question. Yeah, it makes a lot of sense now . .I guess I just missed the details.