ochem questions

[dcl222]

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Problem 1

Can someone walk me through this mechanism? KOH is a base so I believe the alpha hydrogen is removed (...enolate followed by nucleophilic attack) and the CN is attached

Problem 2

and this mechanism...the answer is A
I got after the first arrow, B...but not sure what the second arrow will do

Any guidance is appreciated!!

 

[Orgodox]

Problem 1

Can someone walk me through this mechanism? KOH is a base so I believe the alpha hydrogen is removed (...enolate followed by nucleophilic attack) and the CN is attached
!

Yea you form an enolate (keep in mind there are two possible enolates to form) then the - charge which is partially residing on the carbon attacks the c triple bonded to the N and the lone pair moves onto the N making it negative which then reforms the triple bond with Carbon and kicks off the K

 

[dcl222]

Yea you form an enolate (keep in mind there are two possible enolates to form) then the - charge which is partially residing on the carbon attacks the c triple bonded to the N and the lone pair moves onto the N making it negative which then reforms the triple bond with Carbon and kicks off the K

I'm following what you are saying and I got this...

 

[Orgodox]

Problem 2

and this mechanism...the answer is A
I got after the first arrow, B...but not sure what the second arrow will do

Any guidance is appreciated!!

This ones hard to explain without drawing the mech but first you get the product in B like you said. Now keep in mind, we always have water around Now, since we are in acid protonate the Double bonded O. Heres the KEY STEP!! A water attacks the postion that is doubly allylic and the bond breaks swinging up onto the OH+ and then back down to kick off the OEt.
From here its easy to finish out, just hydrate the remaining one which basically exchanges an Et for an Oh

 

[dcl222]

is this a correct (+/- the small steps) mechanism?

1. OEt's replaced with OH's (H2O) after protonation of the Carbonyl
2. 1,3 Dicarboxylic acid loses CO2

 

[Orgodox]

is this a correct (+/- the small steps) mechanism?

1. OEt's replaced with OH's (H2O) after protonation of the Carbonyl
2. 1,3 Dicarboxylic acid loses CO2

Yep! When I woke up I was like I think the problem had a betaketo acid which should have been a decarboxylation! So I looked at it again, first hydrate it then decarboxylate then simple keto-enol tautomerization and there you have it. Sorry was really tired last night wasnt thinking straight. Good luck

 

[Doa110]

Problem 1

Can someone walk me through this mechanism? KOH is a base so I believe the alpha hydrogen is removed (...enolate followed by nucleophilic attack) and the CN is attached

Problem 2

and this mechanism...the answer is A
I got after the first arrow, B...but not sure what the second arrow will do

Any guidance is appreciated!!

Problem B: 1) This is the general mechanism for diethey ester synthesis, which is: diethyl ester + (NaOET& R'X)....>alkylation at the alpha carbon.
2) Then through Heat&acid...............>decarboxylation leading to acetic acid, substituted by R'.
*The base used and the alkyl groups of esters are usually the same.


Also for elimination purposes; Whenever we have ester groups undergoing heat, we should think that it will broken down to something+carboxylic acid through decarboxylation. So from there, you can at least eleminate some of the wrong answers.
2

 

[aquafreshlovin]

can somebody please draw out the problem #1? i still don't get it.