November 12, 2024, 07:50:48 PM
Forum Rules: Read This Before Posting


Topic: Undergraduate Problem of the Week - 12/2/09  (Read 6368 times)

0 Members and 1 Guest are viewing this topic.

Offline Scatter

  • Regular Member
  • ***
  • Posts: 62
  • Mole Snacks: +3/-1
  • Gender: Male
Undergraduate Problem of the Week - 12/2/09
« on: December 02, 2009, 12:51:35 PM »
So I'm jealous that the graduate forum gets problems of the week, so I thought I'd post this for undergrads who want to try a synthesis for fun.  This will probably be easy for a lot of people on here, but for people who have only started getting their feet wet with organic synthesis (like me) this one might be somewhat of a challenge.

Enjoy!  :)

Design a synthesis for the transformation of 1-butyne to 3-octyn-6-ol using 1-butyne as the only source for carbons.  
You can just list the reagents and what's going on in each synthetic step if you want, but bonus points if you post a complete (or as close to complete as you can) arrow pushing mechanism.


Offline azmanam

  • Chemist
  • Sr. Member
  • *
  • Posts: 1416
  • Mole Snacks: +160/-24
  • Mediocrity is a handrail -Charles Louis d'Secondat
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #1 on: December 02, 2009, 12:57:12 PM »
Well done.  Great idea, and good problem.  I won't spoil the fun, but do encourage other undergrads to try the problem.   Lots of fun for all :)
Knowing why you got a question wrong is better than knowing that you got a question right.

Offline Scatter

  • Regular Member
  • ***
  • Posts: 62
  • Mole Snacks: +3/-1
  • Gender: Male
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #2 on: December 02, 2009, 01:01:20 PM »
Glad to see the problem of the week guru approves. ;)

Offline nj_bartel

  • Sr. Member
  • *****
  • Posts: 1487
  • Mole Snacks: +76/-42
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #3 on: December 02, 2009, 04:45:40 PM »
Cool idea, I might make some of these too if you don't keep up with it :P

Offline Scatter

  • Regular Member
  • ***
  • Posts: 62
  • Mole Snacks: +3/-1
  • Gender: Male
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #4 on: December 02, 2009, 05:01:10 PM »
Neat!  Well, I'm gonna guess that most undergrads on this board usually only want help with homework, but I encourage anyone who even thinks they might be able to do this problem to try it (hints are available).  Doing these will seriously help you in your coursework.  Synthesis problems are already helping me a lot.

Offline nj_bartel

  • Sr. Member
  • *****
  • Posts: 1487
  • Mole Snacks: +76/-42
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #5 on: December 04, 2009, 12:17:03 AM »
Well, I guess I'll give one idea.  Deprotonate the alkyne with sodium amide and SN2 it on the acetal of 1-bromo-2-butanol, hydrolyze the acetal with aqueous acid, then reduce the ketone with borohydride.

Offline Oxy

  • Regular Member
  • ***
  • Posts: 17
  • Mole Snacks: +2/-0
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #6 on: December 04, 2009, 02:43:59 AM »
In my opinion:

Offline wing0714

  • Very New Member
  • *
  • Posts: 1
  • Mole Snacks: +0/-0
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #7 on: December 04, 2009, 09:23:26 AM »
Good idea! And here I am to support this wonderful problem~~~

Offline nj_bartel

  • Sr. Member
  • *****
  • Posts: 1487
  • Mole Snacks: +76/-42
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #8 on: December 04, 2009, 12:21:10 PM »
Can't modify my post, misread the problem :)  Disregard.  I like the last solution.

Offline Scatter

  • Regular Member
  • ***
  • Posts: 62
  • Mole Snacks: +3/-1
  • Gender: Male
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #9 on: December 04, 2009, 01:01:50 PM »
Oxy has it.  Though, can H20 alone be used to protonate in the last step?  I had HCl in H20.  I thought H20 alone wouldn't be acidic enough... Someone correct me if I'm wrong on that point, but for all intensive purposes you recognized that the last step is protonation, so congrats.

Offline nj_bartel

  • Sr. Member
  • *****
  • Posts: 1487
  • Mole Snacks: +76/-42
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #10 on: December 04, 2009, 01:36:57 PM »
It would work moderately well to protonate in that manner.  Weak acid or dilute strong acid would probably be better though.

Offline Oxy

  • Regular Member
  • ***
  • Posts: 17
  • Mole Snacks: +2/-0
Re: Undergraduate Problem of the Week - 12/2/09
« Reply #11 on: December 04, 2009, 09:25:37 PM »
Oxy has it.  Though, can H20 alone be used to protonate in the last step?  I had HCl in H20.  I thought H20 alone wouldn't be acidic enough... Someone correct me if I'm wrong on that point, but for all intensive purposes you recognized that the last step is protonation, so congrats.
Alcohols have pKa ~15 (ethanol), and H2O ~14, not a much difference. Alkoxides dissolve well in water, but not the same with most of alcohols. They will seperate into two phases. So I think we can use H2O only to protonate this alkoxide. At the end, I agree that dilute acid is better ;).

Sponsored Links