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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Jennifer010576 on April 28, 2005, 10:48:05 PM

Title: synthesis of 3-phenyl propanal (from butyl bromide)
Post by: Jennifer010576 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??

Title: Re:synthesis of 3-phenyl propanal (from butyl bromide)
Post by: AWK on April 29, 2005, 01:15:45 AM

http://www.orgsyn.org/orgsyn/prep.asp?prep=cv7p0451

Title: Re:synthesis of 3-phenyl propanal (from butyl bromide)
Post by: Jennifer010576 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?

Title: Re:synthesis of 3-phenyl propanal (from butyl bromide)
Post by: movies 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!

Title: Re:synthesis of 3-phenyl propanal (from butyl bromide)
Post by: dexangeles on April 29, 2005, 06:48:00 PM

Quote from: Jennifer010576 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).

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

Title: Re:synthesis of 3-phenyl propanal (from butyl bromide)
Post by: Jennifer010576 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???

Title: Re:synthesis of 3-phenyl propanal (from butyl bromide)
Post by: movies 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.

Title: Re:synthesis of 3-phenyl propanal (from butyl bromide)
Post by: dexangeles 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?

Title: Re:synthesis of 3-phenyl propanal (from butyl bromide)
Post by: Jennifer010576 on April 30, 2005, 05:47:49 PM

I got it figured out guys!

Thanks for all the *delete me*

Jenn

Title: Re:synthesis of 3-phenyl propanal (from butyl bromide)
Post by: dexangeles on May 01, 2005, 04:24:16 AM

see, now you learned and will remember it ;)

you welcome