July 01, 2022, 07:11:05 PM
Forum Rules: Read This Before Posting


Topic: Mysterious Isomer of Bromo-3-methylpentane  (Read 2316 times)

0 Members and 1 Guest are viewing this topic.

Offline mucker973

  • Regular Member
  • ***
  • Posts: 11
  • Mole Snacks: +0/-0
Mysterious Isomer of Bromo-3-methylpentane
« on: May 01, 2022, 07:23:33 AM »
I am studying chemistry at uni and I had a question which asked me write the skeletal formula of all 3 isomers of the above compound. I worked them out myself, then I went and researched them on the net to confirm I was correct. But I came up with a 4th isomer myself and can't find the flaw in my logic. I cannot find this 4th isomer anywhere on the Internet so I am confident I am wrong in this, but I just want someone to explain to me where my logic is flawed. Here are the facts what I was presented with:

chemical formula: C6H13Br

first isomer - 1-Bromo-3-methylpentane

This has the Br element hanging off the end of the chain
second isomer - 2-Bromo-3-methylpentane

This has the Br element hanging off the 2n or 4th carbon
third isomer - 3-Bromo-3-methylpentane

This has the Br element coming off the 3rd carbon in the opposite direction of double carbon branched chain.

I came up with a 4th, it is the same structure as the 3rd isomer but instead of the Br being where it is there, I had it on the opposite side - at the very end of the C-C branch.

Why is this not a valid isomer?

Offline mucker973

  • Regular Member
  • ***
  • Posts: 11
  • Mole Snacks: +0/-0
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #1 on: May 01, 2022, 07:27:04 AM »
I bit more context to anticipate some answers. I know the opposite has a CH3 there. My understanding is that you can just replace one H with a Br though (which is what is done for all other isomers)

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27120
  • Mole Snacks: +1761/-405
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #2 on: May 01, 2022, 08:55:55 AM »
You mean like that?
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline mucker973

  • Regular Member
  • ***
  • Posts: 11
  • Mole Snacks: +0/-0
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #3 on: May 01, 2022, 10:00:40 AM »

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27120
  • Mole Snacks: +1761/-405
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #4 on: May 01, 2022, 11:13:47 AM »
Can you list the question exactly as it was asked? C6H13Br has many more isomers, for some reason all you listed have one tertiary carbon, which makes me think we are not told everything.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline mjc123

  • Chemist
  • Sr. Member
  • *
  • Posts: 2008
  • Mole Snacks: +290/-12
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #5 on: May 01, 2022, 12:23:58 PM »
If you were asked for the structural isomers of "bromo-3-methylpentane", those are the three. The fourth you identified would not be called "bromo-3-methylpentane" but "3-bromomethylpentane".

Offline mucker973

  • Regular Member
  • ***
  • Posts: 11
  • Mole Snacks: +0/-0
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #6 on: May 01, 2022, 09:53:17 PM »
If you were asked for the structural isomers of "bromo-3-methylpentane", those are the three. The fourth you identified would not be called "bromo-3-methylpentane" but "3-bromomethylpentane".

ok, but why?

Offline mucker973

  • Regular Member
  • ***
  • Posts: 11
  • Mole Snacks: +0/-0
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #7 on: May 01, 2022, 09:55:31 PM »
If you were asked for the structural isomers of "bromo-3-methylpentane", those are the three. The fourth you identified would not be called "bromo-3-methylpentane" but "3-bromomethylpentane".
There are 2 parts to the question. The first one, i answered:

3-Methylpentane is a colourless liquid with a characteristic smell that reacts with bromine liquid (a diatomic molecule) in the presence of a catalyst. A bromo-3-methylpentane liquid compound is formed through the substitution of one hydrogen with bromine.

Write a balanced chemical equation for this reaction and explain if it requires balancing. Hydrogen bromide gas is also a product of this chemical reaction. Note: ignore the presence of the catalyst.


Then the second part:

Bromo-3-methylpentane has three isomers: 1-Bromo-3-methylpentane, 2-Bromo-3-methylpentane, 3-Bromo-3-methylpentane. Draw the skeletal formula of the isomers and write the chemical formula for each isomer.

Offline mjc123

  • Chemist
  • Sr. Member
  • *
  • Posts: 2008
  • Mole Snacks: +290/-12
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #8 on: May 02, 2022, 03:03:13 PM »
Quote
ok, but why?
(1-, 2- or 3-)bromo-3-methyl pentane is a pentane with two substituents - a bromine atom and a methyl group. 3-bromomethylpentane has one substituent, a bromomethyl (CH2Br) group. (Incidentally, I don't see why it shouldn't be one of the products of the bromination reaction.)

Offline mucker973

  • Regular Member
  • ***
  • Posts: 11
  • Mole Snacks: +0/-0
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #9 on: May 02, 2022, 08:14:06 PM »
So... no one knows the answer to this?

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27120
  • Mole Snacks: +1761/-405
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #10 on: May 03, 2022, 02:50:38 AM »
You were already given the answer - according to IUPAC naming rules compound you have suggested is NOT bromo-3-methylpentane but something else.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline mucker973

  • Regular Member
  • ***
  • Posts: 11
  • Mole Snacks: +0/-0
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #11 on: May 03, 2022, 06:27:14 AM »
You were already given the answer - according to IUPAC naming rules compound you have suggested is NOT bromo-3-methylpentane but something else.

yep but then I was asking why it becomes a different compound just because the Br atom is on the position it is. Didn't get an answer on that one?

Offline mjc123

  • Chemist
  • Sr. Member
  • *
  • Posts: 2008
  • Mole Snacks: +290/-12
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #12 on: May 03, 2022, 03:51:40 PM »
Yes you did. If you didn't understand it or otherwise found it unsatisfactory, say why.

Offline Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27120
  • Mole Snacks: +1761/-405
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #13 on: May 03, 2022, 04:13:20 PM »
Check the naming rules.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline mucker973

  • Regular Member
  • ***
  • Posts: 11
  • Mole Snacks: +0/-0
Re: Mysterious Isomer of Bromo-3-methylpentane
« Reply #14 on: May 04, 2022, 11:45:25 PM »
Ok, so I think it is because I don't understand the naming rules. I haven't covered that topic yet in my studies, can you direct to a link which explains that?
thanks,

Sponsored Links