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Organic Chemistry

Blazing goIITian

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24 Jan 2008 18:26:43 IST

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Nomenclature-simple but doubful

Engineering Entrance , Medical Entrance , AIPMT , JEE Main , AIIMS , JEE Advanced , Chemistry , Organic Chemistry

in the nomenclature of haloalkanes,which one shud b given more preference:Cl or Br.how do v know it?

i got this Question in my exam:

Cl-CH2-CH2-CH2-Br.

i wrote it as 1-bromo,4-chloro propane.

is it rite???????

!!!!!!!!!!!!!

Comments (11)

Brad

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Joined: 9 Sep 2007

Posts: 647

24 Jan 2008 18:57:56 IST

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I think you are correct .Among the different halogens

preference is given alphabetically that is Br is preferred

over Chlorine which is preferred over Fluorine which is

further preferred over Iodine.

So the name of the compound is 1-bromo,3chloro propane

Ashish

Scorching goIITian

Joined: 3 Dec 2006

Posts: 223

24 Jan 2008 19:03:04 IST

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Hiiiiii

You are right. In case of two substituent groups that with equal preference and equal locants in the various options that are possible, the one higher up the alphabetical order is supposed to be listed first and given the lower locant.

Hope it helped!

varsha valli g.

Blazing goIITian

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Posts: 515

25 Jan 2008 17:50:21 IST

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thanx a lot!!!
but i read in a book that preference should be given to the heavier one.is it correct?
!!!!!!!!

Ashish

Scorching goIITian

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25 Jan 2008 17:52:29 IST

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I think not. Preference is given to the one higher up the alphabetical order only.

Ashwin R

Blazing goIITian

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25 Jan 2008 21:33:54 IST

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hello........there is only 3 carbon atoms
how can it be 1 -bromo,4chloro propane...
shouldn't it be 1-bromo,3-chloro propane

anand bhanushali

Blazing goIITian

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25 Jan 2008 22:54:11 IST

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there r 3C hence propane
it does not matter whether we write Bromo first or vice versa
but for sake of convenience we just take it in alphabetical order

Ashwin R

Blazing goIITian

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26 Jan 2008 11:34:06 IST

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sorry bharathi....
i am afraid you are wrong......
according to iupac the substituents should always be arranged in
alpabetical order......
there is a system that is given by an authority...... and we are suppose to follow it......

Faiz Ameer

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Joined: 13 Jan 2008

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26 Jan 2008 11:50:16 IST

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I agree with crack....

We should follow alphabetical order.It is there latest IUPAC naming system

k harita

Cool goIITian

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30 Jan 2008 19:32:09 IST

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the answer is 1-bromo 3-chloro propane.......

saurabh panda

Cool goIITian

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31 Jan 2008 13:03:04 IST

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crack is right but

what if an nitro grp is present which one will be prefered

no2 because of alphabet or because of heaviness

Learner .

Blazing goIITian

Joined: 5 Nov 2007

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31 Jan 2008 16:56:29 IST

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There is a list of priority for functional groups...btw nitro and halo you'll have to check that and name accordingly..

The alphabetical order for functional groups comes into play only when you have different atoms of the same group...eg in halo, chloro,bromo have same priority,so here we see alphabetical order

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