October 17, 2019, 02:09:16 PM
Forum Rules: Read This Before Posting


Topic: multiple reactions and organic concepts questions  (Read 5245 times)

0 Members and 1 Guest are viewing this topic.

Offline 113zami

  • Regular Member
  • ***
  • Posts: 33
  • Mole Snacks: +1/-0
multiple reactions and organic concepts questions
« on: June 18, 2008, 12:25:01 PM »
http://i274.photobucket.com/albums/jj243/113zami/orgodd0001.jpg

1)the answer to the above reaction is B, I was unable to find it in my text book, does this reaction also work the same way with the other halogens or only the Cl2?  does it also work with aldehydes the same way ( ie just replace the alpha Hydrogens)?

http://i274.photobucket.com/albums/jj243/113zami/orgodd0002.jpg
2) is this group meta or ortho/para directing, and if it's ortho/para directing, is it activating or deactivating.?
I think it should be meta due to the oxygens which are electron withdrawing, am I correct?

3)Between tertiary non allylic and primary allylic carbocation which one is more stable?I know allylic makes you more stable because of resonance but this is primary allylic vs. TERTIARY carbocation, not just a primary one, so I don't know which to choose??

4)Why will tertiary alcohols dehydrate faster than secondary or primary alcohols? Is it because when you dehydrate this is an elimination reaction and elimination reactions always favor the more substituted product?

5)Which substituents will make the benzene more acidic, halogens or meta directing deactivators? I think the halogones should make them more acidic since they're more electron withdrawing than any meta directing group, correct?

6)More intermolecular forces will increase the freezing point, because it's easier to get to the solid state, correct?

http://i274.photobucket.com/albums/jj243/113zami/orgodd0005.jpg
7) the correct answer  is A but I don't understand why is it not E ? this is how the D2O reaction with benzene is shown in my text  (but they don't give a mechanism for it)
http://i274.photobucket.com/albums/jj243/113zami/orgodd0004.jpg

that's why I chose E, but is it wrong?!
and also what if the substituent on the benzene was an aldehyde, whould the Deuterium take the place of the H on the aldehyde?? 
what if there were other substituents (other than aldehyde and ketone) on the benzene with that D2O reagent, how would they react?? I am clueless 
 
your help is GREATLY appreciated
« Last Edit: June 18, 2008, 12:37:21 PM by 113zami »

Offline spirochete

  • Chemist
  • Full Member
  • *
  • Posts: 501
  • Mole Snacks: +48/-9
  • Gender: Male
Re: multiple reactions and organic concepts questions
« Reply #1 on: June 18, 2008, 06:17:19 PM »
1) This is alpha halogenation of a ketone under acidic conditions.  It should be in your textbook somewhere, perhaps in the same chapter as condensations or near that chapter.  Here's a wikipedia page I found http://en.wikipedia.org/wiki/Ketone_halogenation.  Yes it works with other halogens.

2) So the connection to the benzene ring is at one of the carbons sticking off the ring?  That is an unusual subsituent.  In that case you would have some hyperconjugation from the adjacent SP3 carbon, plus some minor inductive electron withdrawing effects from the oxygens.  Normally we'd expect an oxygen to donate electron density through resonance but they obviously can't because the SP3 carbon gets in the way.  Overall it's difficult to say what the net effect would be.

If i'm wrong about the connection you should redraw it with the benzene ring.

3) This is a good question because it's not obvious intuitively. It should be in your book somewhere.  It turns out secondary and primary allylic are about equal in energy, and tertiary and substituted allylic are about equal.  A good organic book should have this in it somewhere.  Mine had it with the section on Kinetic Vs. Thermodynamic control of addition to conjugated alkenes.

4) Write out the whole mechanism and you'll figure it out.

I'll let somebody else do 5-7.


 
I'm an online organic chemistry tutor and teacher. I have a Master's in organic chemistry, and have years of experience as a TA and teacher. Visit my website http://www.organicchemistrysolutions.com for more information.

Offline vhpk

  • Full Member
  • ****
  • Posts: 259
  • Mole Snacks: +12/-25
  • Gender: Male
Re: multiple reactions and organic concepts questions
« Reply #2 on: June 18, 2008, 11:41:12 PM »
Quote
5)Which substituents will make the benzene more acidic, halogens or meta directing deactivators? I think the halogones should make them more acidic since they're more electron withdrawing than any meta directing group, correct?

Quote
6)More intermolecular forces will increase the freezing point, because it's easier to get to the solid state, correct?
Increase the intermolecular force, the freezing point ( melting point) increase because the energy required to break the bond between molecules increase
Quote
7) the correct answer  is A but I don't understand why is it not E ? this is how the D2O reaction with benzene is shown in my text  (but they don't give a mechanism for it)
H in CH3 group is called alpha hydrogen it can be easily replaced by D so the main product is A
Genius is a long patience

Offline 113zami

  • Regular Member
  • ***
  • Posts: 33
  • Mole Snacks: +1/-0
Re: multiple reactions and organic concepts questions
« Reply #3 on: June 19, 2008, 12:29:21 PM »
thanks alot for helping

vhpk i think you forgot to answer #5 can you please reply 

Offline macman104

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1645
  • Mole Snacks: +168/-26
  • Gender: Male
Re: multiple reactions and organic concepts questions
« Reply #4 on: June 19, 2008, 02:50:41 PM »
You mean, which will make the hydrogens on the benzene more acidic?

If that is the case, while it is true that the halogens will have an electron withdrawing effect, many meta-directors have resonance on their side.

Draw the resonance structures for Nitrobenzene and Chlorobenzene after you remove a hydrogen and see how the charge is more stabilized by the Nitrobenzene.

Sponsored Links