Mass spectometry in structural and stereochemical problems—CLXVIII. Effect of fluorine substitution on the McLafferty rearrangement of aliphatic ketones.

✍ Scribed by Wayne Carpenter; A. M. Duffield; Carl Djerassi

• Publisher: John Wiley and Sons
• Year: 1969
• Tongue: English
• Weight: 365 KB
• Volume: 2
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210020310

✦ Synopsis

The mass spectra of aliphatic ketones are drastically altered following substitution of a trifluoromethyl entity adjacent to the carbonyl group (I1 and 111) or attachment to the y-carbon atom (V). Loss of the trifluoromethyl group by a-cleavage far exceeds the alternative elimination OF an alkyl radical. Virtually complete repression of the McLafferty rearrangement process (I + a ) occurs when a CF, group is attached to the y-carbon atom. A fluorine atom is not transferred in lieu of hydrogen in the McLafferty rearrangement as demonstrated by the mass spectrum of 1,1,1,7,7,7-hexafluoroheptan-4-one (IV). Rationalization for these results are presented as is a description of the syntheses of several hitherto unknown fluorinated ketones. * For part CLXVII see R. Brandt and C. Djerassi, Helv. Chinz. , 'fa in press. t We wish to thank the National Institutes of Health of the US Public Health Service (Grant No. 1 Recipient of a Senior Postdoctoral Fellowship from the US Naval Weapons Center, China Q J. Beauchamp, private communication.

AM-04257) for financial support. Lake, California.