Organic Chem Reaction Mechanisms

[bennettb6]

So I'm preparing for my Organic final by looking at old tests and trying to figure out what I did wrong. Here's a couple things I had trouble with, if you know how to solve any of these the help would be greatly appreciated.

 

1. Draw the product and a mechanism for the following reaction

 

3-ethyl-3-pentanol <--(in the presence of H⁺)--> (blank) + H₂O

 

2. Propose a method to prepare compound B from compound A

 

a. Compound B is trans-1-2-cyclohexanediol, compound A is cyclohexanediol

 

b. I don't know how to name these, but both compounds are a benzene with an ethanol group. The difference is that the OH is on the first CH₂ of the ethyl in compound A and the second CH₂ in compound B.

 

For part a I tried using H⁺ to remove the OH and then osmium tetroxide to add two. For b I used H⁺ to remove the OH group again and did a hydroboration. Both were marked wrong though I think I did the second one wrong, as in the intermediate he drew a double bond on the end of the ethyl group where I did not have one. I'm not sure why he did this so if someone can explain that would be awesome as well

[evern]

So I'm preparing for my Organic final by looking at old tests and trying to figure out what I did wrong. Here's a couple things I had trouble with, if you know how to solve any of these the help would be greatly appreciated.

 

1. Draw the product and a mechanism for the following reaction

 

3-ethyl-3-pentanol <--(in the presence of H⁺)--> (blank) + H₂O

 

 

- OH is protonated

- h2o is lost leaving a +ve charge on a 3* C

- +ve does not migrate due to stability due to hyperconjugation

- depending on media product is a combination of (an alcohol - minor since h+ media) and an alkene.(namely 3-ethyl pent-2-ene)

 

As for the second part could you please attach picture of the compounds because I doubt trans cyclohexane alkenens are stable enough to use in sythesis.

Edited December 22, 2011 by evern

[Suxamethonium]

Im only new to this forum but I think I can help you out a bit.

 

For 2 part a. In sumary:

 

A --> B

 

Cyclohexanediol > E-1,2-cyclohexanediol

 

Compund A is vague- it could be 1,1-cyclohexanediol or Z-1,2-cyclohexanediol. Or perhaps even it could just be cyclohexanol? Either way I feel the easiest way to get a trans diol would be to go via an epoxide intermediate. Thats all I'll say for now, but can help if you get stuck again.

 

As for part b, they sound like 1- and 2-phenylethanols. Dehydration to the alkene would be my first move- and then deside on whether you want markovnikov or anti-markovnikov addition.

 

Hopefully that helps you out in time