Identifying SN1, SN2, E1, and E2 Reactions in Organic Chemistry

[phy]

Hi everyone. I need help with some organic chemistry. When I see a reaction, how do I tell whether it is SN1, SN2, E1, or E2? Also, what is it about a nucleophile that makes it good or bad? Thanks in advance.

 

[GCT]

The term nucleophile usually pertains to the SN2 reaction.

Your organic chemistry book should have sufficient information for your question.

The important factors are whether the carbon compound is 1,2,3 (primary, secondary etc...), the strength of the base (in the case of the E reactions and SN1 reactions; in the case of SN2 it is nucleophile), and the solvent used.

It shouldn't be too difficult. Ask questions if you have any specific problems in understanding.


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[phy]

I read my textbook and i don't quite understand how to differentiate between the four reactions. What is it in the chemical equation that I look for? Please help.

 

[Chemicalsuperfreak]

I'm sensing that you really didn't read the textbook and now you're panicking. Why? Because the differences between substitution and elimination reactions are quite significant.

Why don't you give us your textbook's definitions of Sn1, Sn2, E1, and E2 and then we'll help you clear up what you don't understand.

 

[phy]

No I read the textbook. I was working with a few friends of mine and they taught me how to complete reactions and the mechanisms involved. I even went to see a tutor and she said the same thing. I know how to complete reactions when I'm told what type of reaction it is. I don't know how to identify the type of reaction.

 

[GCT]

Well, elimination consist of a transformation from an alkyl halide to an alkene (since you're at the beginnings of the book this will have to do). Substitution is exactly what the term implies, simply a subtitution reaction. The 2 or 1 is consequential of the rate law. Again here are the distinguishing factors

-the strength of the base which can also be a solvent, in that case it would act as a moderately strong base and in the case of SN2 reactions it would be called a nucleophile; as you may guess you would want to use a "nucleophile" and not a strong base if you wish to persist with the SN2 reaction.

-the degree of steric hinderance

-the temperature of the reaction

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[aychamo]

Aye, look at the temp. If its like 25'C, its going to be SN, if its like 100'C its going to be E.