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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: bc_juno on April 18, 2008, 12:23:35 AM

Title: SYNTHESIS OF 2,3,4-TRIMETHYLPENTAN-3-OL FROM ETHANOL
Post by: bc_juno on April 18, 2008, 12:23:35 AM

Hey all,

I have to figure out how to synthesize 2,3,4,-trimethylpentan-3-ol from ethanol using addition, substitution, and elimination using the least number of steps. I need to find the related equations...I am new to organic chem, your help would be much appreciated!!! thanks in advance

Title: Re: SYNTHESIS OF 2,3,4-TRIMETHYLPENTAN-3-OL FROM ETHANOL
Post by: english on April 18, 2008, 12:48:54 AM

Well, there are several ways to synthesize things like this (almost endless possibilities).

What's the simplest carbon skeleton you can start with?  Acetylene?

Title: Re: SYNTHESIS OF 2,3,4-TRIMETHYLPENTAN-3-OL FROM ETHANOL
Post by: bc_juno on April 18, 2008, 02:49:39 PM

It has to be synthesized with Ethanol as the only source of carbon and I have to use Addition, Elimination, and substitution. Also, C-C bonds can only be made using Grignard reagents.

Title: Re: SYNTHESIS OF 2,3,4-TRIMETHYLPENTAN-3-OL FROM ETHANOL
Post by: shelanachium on April 18, 2008, 04:12:47 PM

One possibility:

CH3CH2OH ----> CH3CO2H (oxidation)

CH3CO2H + CH3CH2OH ---> CH3COOCH2CH3 + H2O (esterification)

Then reaction of 2 moles of isopropyl Grignard reagent with the ester - a standard method of making a teriary alcohol.

CH3COOCH2CH3 + 2 (CH3)2CHMgBr ---> (CH3)2CH-C(OH)CH3-CH(CH3)2 + MgBr2 etc.

                                                        2,3,4 trimethylpentan-3-ol

But no elimination step!

Title: Re: SYNTHESIS OF 2,3,4-TRIMETHYLPENTAN-3-OL FROM ETHANOL
Post by: Ak on April 18, 2008, 06:11:43 PM

I was told that this could be made from pentan-3-ol, so this may sound stupid to you pros...but how do you synthezise pentan-3-ol from ethanol? Thanks in advance

Title: Re: SYNTHESIS OF 2,3,4-TRIMETHYLPENTAN-3-OL FROM ETHANOL
Post by: sjb on April 20, 2008, 03:30:19 PM

Well, consider what shelanachium has posted, look at the differences in the carbon chains, and see how they're put together.

Perhaps.

Title: Re: SYNTHESIS OF 2,3,4-TRIMETHYLPENTAN-3-OL FROM ETHANOL
Post by: nox on December 26, 2008, 03:45:12 PM

I apologize for reviving a dead topic, but I stumbled across this question the other day while being bored and it intrigued me

The original question can be found at http://www.utm.utoronto.ca/~w3chm140/examquestions07-08.pdf (http://www.utm.utoronto.ca/~w3chm140/examquestions07-08.pdf) it is question #8

I think the hardest part here is that the ONLY source of carbon is from ethanol, and no matter how hard I try I just can*not* create the branching required in the product, and this is very frustrating (and quite embarassing since I've already done org 2 + 3 :( ) The question essentially boils down to this:(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fimg522.imageshack.us%2Fimg522%2F4060%2Fsynthesisxf7.png&hash=940dbf5e27e9a61c502a3a70352391dd24733bf5)

I mean I did manage to come up with creating an isopropanol unit from ethanol but it's too long and too extreme and overall yield would likely be crap:
EtOH + SOCl2 + pyridine + heat ---> ethylene + ozone ---> formaldehyde x 2 + NaBH4 ----> MeOH x2 + SOCl2 ---> methyl chloride + Mg ---> MeMgCl + acetaldehyde (from EtOH oxidation with PCC) ---> isopropanol

Title: Re: SYNTHESIS OF 2,3,4-TRIMETHYLPENTAN-3-OL FROM ETHANOL
Post by: azmanam on December 26, 2008, 11:37:38 PM

Quote

ethylene + ozone ---> formaldehyde x 2

That's good.  I like that.

You can use that synthesis of isopropanol and shelanachium's suggestion on making a tertiary alcohol to make the molecule you've drawn.