Home » Ask & Discuss » Chemistry. » Organic Chemistry « Back to Discussion

Organic Chemistry

Blazing goIITian

Joined:	1 May 2007
Post:	777

12 Feb 2008 12:38:34 IST

0 People liked this

830

Organic chemistry again...

None

The major product obtained by the friedel-crafts reaction of n-butyl bromide with benzene in presence of anhydrous AlCl3 is 1-phenyl butane or 2-phenyl butane????
help reqd. plz...

Share this article on:

Comments (9)

Ankur Verma

Blazing goIITian

Joined: 29 Mar 2007

Posts: 555

12 Feb 2008 12:41:09 IST

Like 0 people liked this

well buddy bod r same coz benzene don hav ny oder group attached to it so when u wld number d number wld b same i.e.

LAMPARD

Blazing goIITian

Joined: 1 May 2007

Posts: 777

12 Feb 2008 12:43:26 IST

Like 0 people liked this

Arrey,in 1st option benzene group is attached to 1st carbon in butane n in 2nd to the 2nd carbon of butane...

Ankur Verma

Blazing goIITian

Joined: 29 Mar 2007

Posts: 555

12 Feb 2008 12:59:21 IST

Like 0 people liked this

arey buddy

if u r saying dat 2nd carrbon den it shld b

1 methyl 2 phenyl bromo propane isn't

n buddy

in acylation/alkylation Br is removed so d product wld b only 1 i.e.

1 phenyl butane

Ankur Verma

Blazing goIITian

Joined: 29 Mar 2007

Posts: 555

12 Feb 2008 13:02:44 IST

Like 2 people liked this

c d mechanism

Friedel-Crafts alkylation

Overview:

The general form of the Friedel-Crafts alkylation mechanism is as follows:

Adding an alkyl halide to the Lewis acid aluminum trichloride results in the formation of an organo-metallic complex. In this complex the carbon attached to the chlorine has a great deal of positive charge character (in fact, for practical purposes when dealing with this reaction, you can think of the partially positive charge as a carbocation).

The pi electrons in a benzene ring are mildly electrophilic, and can attack the partially positive carbon to create a non-aromatic intermediate (note that this intermediate has several resonance structures, so that it is not as unstable as it might appear). Elimination of a proton re-establishes the aromaticity of the ring, and the aluminum trichloride catalyst is regenerated along with a molecule of hydrochloric acid.

A word of caution about this reaction: because the aluminum trichloride generates what can essentially be thought of as a carbocation, rearrangments can occur to produce a more highly-substituted carbocation.

For example: Addition of 1-Chloro-2-Methylpropane to benzene with aluminum trichloride results in the rearranged product, t-butyl benzene, and not the product that you might initially expect (work out the mechanism if you cannot see how that product is attained).

An example of a Friedel-Crafts alkylation:

Ankur Verma

Blazing goIITian

Joined: 29 Mar 2007

Posts: 555

12 Feb 2008 13:04:06 IST

Like 0 people liked this

hope u got it now

do temme if ny oder problem 2

LAMPARD

Blazing goIITian

Joined: 1 May 2007

Posts: 777

12 Feb 2008 13:06:12 IST

Like 0 people liked this

i stil didn get iupac name for 2nd option...

Ankur Verma

Blazing goIITian

Joined: 29 Mar 2007

Posts: 555

12 Feb 2008 13:07:53 IST

Like 0 people liked this

d naming wld b 1 bromo 3 phenyl butane

nitigya

Scorching goIITian

Joined: 5 Dec 2006

Posts: 225

12 Feb 2008 14:51:14 IST

Like 0 people liked this

see lampard

it should be 2nd option(wtver name it has) .

when we use AlCl₃ it is a strong lewis acid. as such it can facilate the formation of a rearranged isomer.

[C---C---C---C^delta(+)]-----Br-----AlCl₃^delta(-)

[C---C---C^delta(+)---CH]-----Br-----AlCl₃^delta(-)

this thing cannot happen with FeCl3 as it is weak and will give an unrearranged product

aatman

New kid on the Block

Joined: 12 Jun 2008

Posts: 24

14 Jan 2009 12:30:47 IST

Like 0 people liked this

oye frank!!
Its definitely 2-Phenyl Butane coz sec. is more stable carbocation than primary.
And F.C. Alkylation involves carbocation generation.....

Quick Reply

Reply

	Some HTML allowed.
	Keep your comments above the belt or risk having them deleted.
	Signup for a avatar to have your pictures show up by your comment
	If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team