[rita87]

Hi eveybody,
does anyone know why HMPA or its equivalents helps second deprotonation of 1,3 dithiane.HMPA was added after the addition of n-Butyl lithium and it has increased the yield of alkylation by 37%.

[azmanam]

It acts as a ligand for lithium.  it dissociates lithium from carbon compounds and helps make the anion a bit more potent.

PS, can I just say that it's almost dangerous that wikipedia says HMPA is 'mildly toxic.'  DO NOT get HMPA on you.  Be VERY careful handling HMPA.

[rita87]

Thanks azmanam

[nj_bartel]

Is it just the fact that it's a carcinogen that can absorb through skin that makes it dangerous?  Fischer msds didn't have anything else that awful that I noticed.

[azmanam]

yup.  that's a problem.  when I was introduced to HMPA, we referred to it as 'cancer in a bottle.'  we like to play the 'not it' game in lab when it's time to distill large quantities of HMPA.

[nj_bartel]

Ah, aright.  Thanks