So I\'ve been working on a Organic Chem Lab and have come to a conclusion that I
ID: 801429 • Letter: S
Question
So I've been working on a Organic Chem Lab and have come to a conclusion that I would like feedback on regarding the accuracy of my assumptions:
2-chloro-2-methylpropane and 2-bromo-2-methylpropane are added to different solvents. The main solvents are isopropyl, ethanol, and acetone. The main solvents are tested separately for each alkyl halide. The concentrations of the solvents when tested are offset by water concentrations. NaOH is added to each of these concentrations to act as either a base or nucleophile.
Acetone (polar aprotic)-NaOH in Acetone acts as a nucleophile-mechanism is SN2
Water (polar protic)-NaOH in water acts as a base-mechanism is E1
Isopropyl (polar protic)-NaOH acts as a base-mechanism is E1
Ethanol (polar protic)-NaOH acts as a base-mechanism is E1
HCl (test solvent)-halides are nucleophiles-the substrate is tertiary-mechanism is SN1
Could someone tell me if I am incorrect or correct in a relatively concise manner in regards to whether the mechanisms I selected are accurate.
Just for giggles, here are my summary notes:
Solvent Polar Protic-SN1 or E1
Solvent Polar Aprotic-SN2 or E2
Nucleophile Strong-SN2
Nucleophile Weak-SN1
Strong Base-E2
Weak Base-E1
NaOH are base in polar protic and a nucleophile in polar aprotic
Explanation / Answer
You are absolutely right with each mechanism.
the carbon at which leaving group is attached is sterically crowded, so there is very less possibility of SN1 or SN2 reaction.
these tertiary butyl compound exist in dynamic equillibrium with their ionic form, as the carbocation is highly stable.
(CH3)3C+ Br- & (CH3)3C+ Cl-
In polar Aprotic solvents OH- acts as a very strong nucleophile. As Na+ is solvated by bulky groups. Br- and Cl- are not able to leave before attack of nucleophile as medium is aprotic.
Hence SN2 mechanism is favoured in polar aprotic medium.
In polar protic medium the ions get solvated, and Carbocation formed immediately undergoes E1 mechanism .
With HCl
as i said the compound exist in dynamic equillibrium with their ionic form . SN1 mechanism .
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