Organic Chemistry problems (help pr0x)

[Ħ]

I've got a problem set due in a few hours with a few questions that are pretty tough. Could someone help me out?




1) If R group is -CH3?(2 products)
2) If R group is -NO2? (1 product)
3) If R group is -CH2CH3, and we add Pd and PR3 and remove KNH2? (1 product)
4) If R group is -CH3 (and Br is converted to NH2), and we change KNH2 to NaNO2, H2O and HCl at 0 C? (1 product, then add heat for another product)


I've got that (1) is nucleophilic aromatic substitution which involves a benzyne intermediate by swapping -Cl for -NH2.


For (2), is that just regular old electrophilic aromatic substitution, where we add -NH2 to the carbon right next to chlorine? That doesn't make sense though, as NH2- is a nucleophile, so I dunno.


For (3), I think that will just swap the -Cl for -NH2? I was originally thinking it would give -OH (that's what in my notes for this reaction), but there's nowhere you would get the -OH.


For (4) I think there's a diazonium ion involved but I dunno what the nucleophile would be that kicks -N2+ out.

[Dr. DTVT]

You got 1) half right.  There are two products.  You need to include the second product.  Since you understood that the reaction goes through a benzyne intermediate, I'm sure you can figure out the other product if you draw the benzyne.

2) When you change R to -NO₂, you now have EWG's instead of EDG's, so when you form the benzyne, you get addition to one site instead of at both sites like you did in 1)

3) Pd cross-coupling reaction

4) Yup, start by making a diazonium ion.  Not all diazonium ions kick off N₂.  Look up the synthesis of methyl orange and see if that give you any ideas.

[TioJorge]

 







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[Ħ]

Thanks doc. I did have to submit it last night but I was able to figure them out in time. We actually made methyl orange in lab, so for (4) I picked the answer that contained a azo group connecting two benzenes.