Comments for Master Organic Chemistry

Comment on The Hofmann and Curtius Rearrangements by James Ashenhurst

James Ashenhurst — Fri, 18 Oct 2024 19:49:52 +0000

In reply to Aadity. We don't use NaI or NaBr for the Hofmann rearrangement because they are not electrophilic sources of halogen. We use Br2 or other sources of electrophilic Br or Cl. I am not aware of an example of using I2 or similar electrophilic I(+) reagents for doing the Hofmann but there is no reason I can see as to why it would not work, although why you'd prefer to use I versus Br I'm not sure

Comment on Selectivity In Free Radical Reactions by James Ashenhurst

James Ashenhurst — Fri, 18 Oct 2024 19:47:07 +0000

In reply to Aadity. Greater selectivity of Br versus Cl. That's why I wrote the article

Comment on The SN2 Mechanism by James Ashenhurst

James Ashenhurst — Fri, 18 Oct 2024 19:46:36 +0000

In reply to Aadity. Published rates indicate that the rate of reaction for methyl halides is roughly 30 times the rate for primary halides (e.g. benzyl chloride) assuming the nucleophile is the same. That's the rough difference in rates.

Comment on OsO4 (Osmium Tetroxide) for Dihydroxylation of Alkenes by James Ashenhurst

James Ashenhurst — Fri, 18 Oct 2024 19:45:37 +0000

In reply to Kelsey.

Hi – great questions. Start with neutral osmium having an oxidation state of zero. Then subtract 1 for every bond to a more electronegative atom (O). In OsO4 there are eight. In the osmate ester there are six bonds to oxygen. This accounts for the difference in oxidation state – it has gone from Os(VIII) to Os(VI)

What happens when the lone pair goes into Os during the [3+2] is that there are an extra pair of electrons on osmium that weren’t there before. We generally don’t draw the lone pairs in on transition metals (because there can be a lot!). But if we know the oxidation state, we can figure it out. The oxidation state is now two less due to that lone pair.

Comment on OsO4 (Osmium Tetroxide) for Dihydroxylation of Alkenes by Kelsey

Kelsey — Fri, 18 Oct 2024 00:07:16 +0000

How do you determine the oxidation state of osmium in the osmate ester form? Also, I would think that the lone pair that went onto osmium during the 3+2 cycloaddition has to be accounted for, but I’m not sure how.

Comment on The SN2 Mechanism by Aadity

Aadity — Thu, 17 Oct 2024 15:55:28 +0000

Thanks for this post! How can we compare the rate of SN2 for chloroethane and benzyl chloride?

Comment on Selectivity In Free Radical Reactions by Aadity

Aadity — Thu, 17 Oct 2024 15:50:38 +0000

2-methyl propane on chlorination (Cl2, hv) gives 1-chloro-2-methyl propane while
bromination (Br2 , hv) gives 2-bromo-2-methyl propane majorly. why?

Comment on The Hofmann and Curtius Rearrangements by Aadity

Aadity — Thu, 17 Oct 2024 15:22:46 +0000

Is it possible to convert an amide into an amine just like Hoffmann rearrangement using NaI instead of NaBr?

Comment on Comparing the SN1 and SN2 Reactions by Kritish Vyas

Kritish Vyas — Mon, 14 Oct 2024 19:52:47 +0000

Thanks for the sn1 and sn2 comparisons

Comment on Partial Reduction of Alkynes With Na/NH3 To Obtain Trans Alkenes by James Ashenhurst

James Ashenhurst — Mon, 14 Oct 2024 16:05:57 +0000

In reply to Sohail. Acetylides can be formed by treating alkynes with NaNH2 in ammonia solution.That's different from Na (sodium metal).