Organic Question-please help!

[hopeful dental]

Hi guys,

Could someone help me understand this question....I won't use verbatim, but basically the question is asking:

If you have an alkane with a methyl group and a halogen on the same carbon accompanied with (let's say) a sodium cyanide in ethanol what would be the results?

A. the retention of absolute configuration
B. the formation of a racemic mixture
C. the elimination of HCL
D. the inversion of absolute configuration
E. the formation of optically inactive products

I picked B because I thought that this reaction would be considered an SN1 reaction because of the protic solvent....thus SN1 reactions give you racemic products.

The correct answer is E.....why E???

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[supraman]

Hi guys,

Could someone help me understand this question....I won't use verbatim, but basically the question is asking:

If you have an alkane with a methyl group and a halogen on the same carbon accompanied with (let's say) a sodium cyanide in ethanol what would be the results?

A. the retention of absolute configuration
B. the formation of a racemic mixture
C. the elimination of HCL
D. the inversion of absolute configuration
E. the formation of optically inactive products

I picked B because I thought that this reaction would be considered an SN1 reaction because of the protic solvent....thus SN1 reactions give you racemic products.

The correct answer is E.....why E???

I believe this is in Kaplan BB, chiral centers come in either R or S. An R will rotate plane-polarized light to a certain degree one way and the S will do the exact amount but opposite way together the net is optically inactive products because of cancellation. However, B is also right, a racemic mixture contains equal amounts of R and S, so I can see why your confused, I guess maybe its because E not only includes B, but states its also inactive....

 

[Danny289]

Hi guys,

Could someone help me understand this question....I won't use verbatim, but basically the question is asking:

If you have an alkane with a methyl group and a halogen on the same carbon accompanied with (let's say) a sodium cyanide in ethanol what would be the results?

A. the retention of absolute configuration
B. the formation of a racemic mixture
C. the elimination of HCL
D. the inversion of absolute configuration
E. the formation of optically inactive products

I picked B because I thought that this reaction would be considered an SN1 reaction because of the protic solvent....thus SN1 reactions give you racemic products.

The correct answer is E.....why E???

I don't like this question, because you can pick the answer B somehow. if there wasn't "E" in answers, for sure the B is correct, think racemic mixture is not meaning optically inactive it can be different percentage of "D" and "L" for example 30% and 70% then it is not optically inactive. Racemic mixture is inactive when it 50-50 for this reason we choose E.
as I said I don't like this question

 

[hopeful dental]

yeah, I don't like this question either....the crazy thing is this is a question from a Kaplan test!!! Oh, well, I'll go back to the Kaplan book and see what's up....thanks for the comments....I appreciate it.

 

[supraman]

beat you

 

[hopeful dental]

huh???? I don't get it..... because of the time?