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Topic: synthesis of 3-phenyl propanal (from butyl bromide)  (Read 17694 times)

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Jennifer010576

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synthesis of 3-phenyl propanal (from butyl bromide)
« on: April 28, 2005, 10:48:05 PM »
I need help with this problem I've literally been struggling over for 6+ hours.
The problem is to outline the synthesis of 3-phenylpropanol from the starting point of benzyl bromide (in three total steps).

My thoughts...
    step 1: prepare a grinard reagent w/ the benzyl bromide.

    step 2: prepare a primary alcohol by reacting the grignard
               reagent w/ formaldehyde.

    step 3: form the aldehyde by oxidizing the primary OH.

My problem...

    I always end up with a 2-phenyl ethanal, instead of
    3-phenyl propanal.

I've also tried going from benzyl bromide - grignard - carboxylic acid - aldehyde...but this has an extra step and still gets me 2-phenyl ethanal.

Any suggestions or what am I doing wrong??

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Jennifer010576

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Re:synthesis of 3-phenyl propanal (from butyl bromide)
« Reply #2 on: April 29, 2005, 10:06:40 AM »
The above website shows...

"The procedure described here is a one-step conversion of (2-chloroethyl)benzene to 3-phenylpropionaldehyde."

This doesn't help me

Any other ideas?


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Re:synthesis of 3-phenyl propanal (from butyl bromide)
« Reply #3 on: April 29, 2005, 01:00:36 PM »
What other electrophiles can you add into with a Grignard reagent?

I think you are forgetting one that will make this problem a snap!

dexangeles

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Re:synthesis of 3-phenyl propanal (from butyl bromide)
« Reply #4 on: April 29, 2005, 06:48:00 PM »
I need help with this problem I've literally been struggling over for 6+ hours.
The problem is to outline the synthesis of 3-phenylpropanol from the starting point of benzyl bromide (in three total steps).

do you want 3-phenylpropanol or 3-phenylpropanal?
if you want propanol then it's 2 steps
propanal is three steps

hint1: you need to add 2 Carbons and formaldehyde only has 1 Carbon
hint2: do Grignard reagents only react with carbonyl containing compounds?

think about hint2 really well
« Last Edit: April 29, 2005, 06:57:47 PM by Ad Majorem Dei Gloriam »

Jennifer010576

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Re:synthesis of 3-phenyl propanal (from butyl bromide)
« Reply #5 on: April 29, 2005, 10:12:39 PM »
Okay...I appreciate the help, but I even more frustrated now...if possible...now it's because I feel like I'm close...but I still don't get it.

This is my first O.Chem class and they only thing we've been explained (so far) is adding formaldehyde to the Grignard, gets a primary alcohol and adding acetanalyde will get a secondary alcohol (but I can't use a secondary).

I'm not sure what else I can add.  It is 3-phenylpropanAL, though...that I need.

Please...more thoughts???

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Re:synthesis of 3-phenyl propanal (from butyl bromide)
« Reply #6 on: April 29, 2005, 11:28:20 PM »
Read through the tutorial here:

http://orac.sunderland.ac.uk/~hs0bcl/org3.htm

It's a couple of pages but the answer is in there.

dexangeles

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Re:synthesis of 3-phenyl propanal (from butyl bromide)
« Reply #7 on: April 30, 2005, 03:09:08 PM »
things to know

1. Grinard reagents, like organolithium have carbanionic character
2. this carbanionic character makes it very basic
3. organometals are a way for carbon-carbon bonds to be synthesized

heres a BIG hint: what do grignard reagents do with epoxides?

Jennifer010576

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Re:synthesis of 3-phenyl propanal (from butyl bromide)
« Reply #8 on: April 30, 2005, 05:47:49 PM »
I got it figured out guys!

Thanks for all the *delete me*

Jenn

dexangeles

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Re:synthesis of 3-phenyl propanal (from butyl bromide)
« Reply #9 on: May 01, 2005, 04:24:16 AM »
see, now you learned and will remember it ;)

you welcome

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