A few posts back, I explored the “benzidine rearrangement” of diphenyl hydrazine. This reaction requires diprotonation to proceed readily, but we then discovered that replacing one NH by an O as in N,O-diphenyl hydroxylamine required only monoprotonation to undergo an equivalent facile rearrangement. So replacing both NHs by O to form diphenyl peroxide (Ph-O-O-Ph) completes this homologous series. I had speculated that PhNHOPh might exist if all traces of catalytic acid were removed, but could the same be done to PhOOPh? Not if it continues the trend and requires no prior protonation at all!
Posts Tagged ‘energy’
Why diphenyl peroxide does not exist.
Monday, April 29th, 2013How to predict the regioselectivity of epoxide ring opening.
Sunday, April 28th, 2013I recently got an email from a student asking about the best way of rationalising epoxide ring opening using some form of molecule orbitals. This reminded me of the famous experiment involving propene epoxide.[cite]10.1021/ja01208a047[/cite]
The mechanism of ester hydrolysis via alkyl oxygen cleavage under a quantum microscope
Tuesday, April 2nd, 2013A sideways look at the mechanism of ester hydrolysis.
Friday, March 29th, 2013The mechanism of ester hydrolysis is a staple of examination questions in organic chemistry. To get a good grade, one might have to reproduce something like the below. Here, I subject that answer to a reality check.
Understanding the electrophilic aromatic substitution of indole.
Sunday, March 3rd, 2013The electrophilic substitution of indoles is a staple of any course on organic chemistry. Indoles also hold a soft-spot for me, since I synthesized not a few as part of my Ph.D. studies.[cite]10.1039/P29750001209[/cite],[cite]10.1039/P29770000281[/cite] The preference for substitution in the 3-position is normally explained using the arrows shown below (position 3=green,2=blue,1=red). Here I explore how these arrows might be interpreted in terms of various quantum mechanical properties.
A to-and-fro of electrons operating in s-cis esters.
Thursday, February 21st, 2013The conformation of acetaldehyde: a simple molecule, a complex explanation?
Friday, February 8th, 2013Consider acetaldehyde (ethanal for progressive nomenclaturists). What conformation does it adopt, and why? This question was posed of me by a student at the end of a recent lecture of mine. Surely, an easy answer to give? Read on …
How does one describe the wavefunction for the π-complex formed from PhNHOPh?
Friday, January 25th, 2013Although have dealt with the π-complex formed by protonation of PhNHOPh in several posts, there was one aspect that I had not really answered; what is the most appropriate description of its electronic nature? Here I do not so much provide an answer, as try to show how difficult getting an accurate answer might be.
The π-complex in the benzidine rearrangement: a molecular orbital analysis.
Friday, January 18th, 2013Michael Dewar[cite]10.1016/S0040-4039(01)82765-9[/cite] famously implicated a so-called π-complex in the benzidine rearrangement, back in the days when quantum mechanical calculations could not yet provide a quantitatively accurate reality check. Because this π-complex actually remains a relatively unusual species to encounter in day-to-day chemistry, I thought I would try to show in a simple way how it forms.