![]() |
![]() |
|||||||
Daphuk_up
(Hive Bee) 03-23-04 01:19 No 496725 |
![]() |
2-phenylbenzimidazole | ||||||
SWID was wondering if anybody had any references other than the ones posted, or theories on the mechanistics of this reduction. SWID is thinking the reaction occurs on a 1:1 molar basis, where one molecule of benzaldehyde plus one molecule of o-phenlyenediamine condese to form PBI + H2 + H2O. Seeing the production of the hydrogen (in H radical form?) shows where the hydrogen is coming from, but doesn't really explain how this is able to add across the double bond. So questions are: 1. Mechanistics? 2. 91% IPA ok? (H2O shouldnt be a problem) 3. this only works if PBI is generated in situ? Since the PBI is isolated during workup, might it be possible to use it as a catalyst w/ hydrogen introduced from an outside source? (SWID is thinking not, be he is often thinking wrong, so). 4. Is inert atmosphere necessary? What about a hydrogen atmosphere? Links, replies, comments, etc very much appreciated. ![]() Drug Chemists are Ta to a good Sm. |
||||||||
![]() |
![]() |
|||||||
![]() |
![]() |
|||||||
Rhodium (Chief Bee) 03-23-04 02:21 No 496740 |
![]() |
I think you have confused your heterocycles | ||||||
When reacting benzaldehyde with phenylenediamine, you get 2-phenyl-benzimidazoline (PBI) through an intermediate imine with the loss of water. No hydrogen is lost. ![]() Upon reacting PBI with a hydrogen acceptor like a nitrostyrene (see Post 352950 (Barium: "Get that double bond without borohydride", Novel Discourse)), the products are the saturated nitroalkane and 2-phenyl-benzimidazole: ![]() The driving force in the reduction is the formation of the aromatic heterocycle (resonance energy) from the aliphatic nitrogen ring in the benzimidazoline. I think the reaction proceeds through some kind of hydride transfer, so no free hydrogen (radical or molecular) is ever formed. The Hive - Clandestine Chemists Without Borders |
||||||||
![]() |
![]() |
|||||||
![]() |
![]() |
|||||||
Daphuk_up (Hive Bee) 03-23-04 02:53 No 496747 |
![]() |
Wonderful! Thanks to the Chief Bee from SWID,... | ||||||
Wonderful! Thanks to the Chief Bee from SWID, this whole reaction makes a LOT more sense now. (SWID was gonna edit and ask why when the two reagents are added they don't release any gaseous hydrogen, now he knows!) ![]() Drug Chemists are Ta to a good Sm. |
||||||||
![]() |
![]() |
|||||||
![]() |
![]() |
|||||||
Daphuk_up (Hive Bee) 03-23-04 03:14 No 496753 |
![]() |
To derive answers | ||||||
To answer SWIDs own questions: 2. No prob, just a bit longer reflux since lower temp. 3. Cannot reuse the recovered imidozole. (Regeneration? Probably not worth it.) 4. Looks like the atmospheric danger is largely from oxygen, oxidizing the -oline to ozole. Drug Chemists are Ta to a good Sm. |
||||||||
![]() |
![]() |
|||||||