May 09, 2021, 11:55:24 AM
Forum Rules: Read This Before Posting


Topic: Problem of the week - 30/04/2012  (Read 9400 times)

0 Members and 1 Guest are viewing this topic.

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 26491
  • Mole Snacks: +1721/-402
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Problem of the week - 30/04/2012
« on: April 30, 2012, 10:22:49 AM »
Simple one, and an open one - that is, I think I know the answer, but I am ready for better solutions.

What is the lightest (lowest molar mass) chiral compound made of C and H only?

What is the lightest chiral compound (no restriction to CH)?

ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline cth

  • Full Member
  • ****
  • Posts: 223
  • Mole Snacks: +36/-8
Re: Problem of the week - 30/04/2012
« Reply #1 on: April 30, 2012, 01:12:11 PM »
What is the lightest (lowest molar mass) chiral compound made of C and H only?

I think it's C5H8:

H3C          H
   \          /
    C=C=C
   /          \
  H           CH3



What is the lightest chiral compound (no restriction to CH)?
Does the compound have to be known and stable, or something more "exotic" would do?

For example, a cyclopropane with 2 trans-substituted lithium atoms C3H4Li2 (I haven't check if this particular compound exists):

     CH2   
     /\
Li-C-C-H
  /      \
 H       Li

Offline fledarmus

  • Chemist
  • Sr. Member
  • *
  • Posts: 1676
  • Mole Snacks: +203/-28
Re: Problem of the week - 30/04/2012
« Reply #2 on: April 30, 2012, 01:44:41 PM »
Personally I was thinking of the ammonia analog NHDT for the smallest chiral compound -

      N
    / | \
   H D T

Of course, at a temperature cold enough to freeze out the umbrella transition...

MW ~ 20

But the methyllithium analog Li-CHDT (MW~21) might be a better choice, being more stably chiral.

Offline sjb

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 3541
  • Mole Snacks: +218/-42
  • Gender: Male
Re: Problem of the week - 30/04/2012
« Reply #3 on: April 30, 2012, 01:51:41 PM »
Personally I was thinking of the ammonia analog NHDT for the smallest chiral compound -

      N
    / | \
   H D T

Of course, at a temperature cold enough to freeze out the umbrella transition...

MW ~ 20

perhaps you can go one further and utilise the 12N isotopologue (or the 10N, if you want really exotic)?

But the methyllithium analog Li-CHDT (MW~21) might be a better choice, being more stably chiral.

Similarly, there are lighter isotopes of Li and C???

Offline AWK

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 7984
  • Mole Snacks: +555/-93
  • Gender: Male
Re: Problem of the week - 30/04/2012
« Reply #4 on: May 01, 2012, 05:51:46 PM »
Quote
But the methyllithium analog Li-CHDT (MW~21) might be a better choice, being more stably chiral.
CH3Li is an ionic compounds, hence  chiral stability of Li-CHDT is questionable.
AWK

Offline fledarmus

  • Chemist
  • Sr. Member
  • *
  • Posts: 1676
  • Mole Snacks: +203/-28
Re: Problem of the week - 30/04/2012
« Reply #5 on: May 01, 2012, 08:08:33 PM »
Quote
But the methyllithium analog Li-CHDT (MW~21) might be a better choice, being more stably chiral.
CH3Li is an ionic compounds, hence  chiral stability of Li-CHDT is questionable.

Not really ionic - carbon-lithium bonds actually have a surprising amount of covalent character. Methyllithium in particular does not tend to dissociate; in both solutions and solids it tends to form aggregate structures with the lithiums in the center and the methyl groups on the outside. This would tend to keep the methyl groups from flipping. At least, I would predict them to be more stable than ammonia...

Offline Ann1234

  • Regular Member
  • ***
  • Posts: 63
  • Mole Snacks: +4/-0
  • Gender: Female
Re: Problem of the week - 30/04/2012
« Reply #6 on: May 05, 2012, 12:37:57 AM »
Simple one, and an open one - that is, I think I know the answer, but I am ready for better solutions.

What is the lightest (lowest molar mass) chiral compound made of C and H only?

for this one so far I have:

                     T
                     /
                D -C*-H
                   /
                  C*H3

* Being C-8 (lowest-mass C isotope I found) both carbons in the molecule. Molar mas is around 25 g/mol.
« Last Edit: May 05, 2012, 01:35:25 AM by Ann1234 »

Offline AWK

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 7984
  • Mole Snacks: +555/-93
  • Gender: Male
Re: Problem of the week - 30/04/2012
« Reply #7 on: May 07, 2012, 02:06:27 AM »
But C-8 has half life of 2.0 x 10−21 s.
If we are talking about chirality we should measure it. in this case and in the case of CHDTLi the measurement is impossible because of stability.
Chirality of CHDTCOOH is known - I think this is the lowest weight molecule for which chirality is proved.
We can expect a stable chirality  for example from CHDTBH2, CHDTCH3 CHDTNH2.
From theoretical point of view CHDT4H should be chiral - 4H shows half life 1.39  × 10−22 s - in this case  8C can also be used.
« Last Edit: May 07, 2012, 02:25:04 AM by AWK »
AWK

Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 26491
  • Mole Snacks: +1721/-402
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Re: Problem of the week - 30/04/2012
« Reply #8 on: May 07, 2012, 09:32:27 AM »
H3C          H
   \          /
    C=C=C
   /          \
  H           CH3

Nice one. I was thinking about 1,3-dimethylcyclopropene, but it has one hydrogen more.

I guess to say which of the other answers is best I should define the question much more precisely first. I was thinking about adding some remarks about stability and "isolability" to the question, but they are not obvious, besides, I have a feeling as long as we don't have a sample of H,D,T substituted compound it is hard to predict if we would be able to separate chiral isomers.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline AWK

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 7984
  • Mole Snacks: +555/-93
  • Gender: Male
AWK

Sponsored Links