tip directly in the cooling bath until crj-stals formed. The molal freezing point constant used for beiizene was 5.12'. The low solubility of N , ~ ' - d i - o - t i ~ l ~ l f c ~ r m a m i dini nliene zeiie allmred determinations (JF frceziiig point depressions
[ "cONTRIBUTION
FROM THE CHEMICAL
in only very dilute solutions where experimental crrors \\-ere comparatively higher, but there is 110 douht about the cluxlitative result. .-'LUSTIS 12, TEXAS
RESEARCH I,ABORATORY,
POLAROID
CORPORATIOX]
1 , l -Difluoro-2-methylpropene, 3,3-Difluoro-2-methylpropene and
3,3-Difluoro-3-chloro-2-methylpropene BY
RICII.4RD
s. CORLEY,SAUL G. COHEX,AIYRO?; s. SIMON.4ND HEKRYT. ~ Y O I . ~ S I X S K I RECEIVED JASL-ARY 3 , 1956
The preparation and iirouerties of CF?-=-C(CH3)?, tives are described
C H I = = C ( C H J ) C H F 2 , CHs:=C(CH3) C F r C I and
R
nuinhcr
cif
dcriva-
As part of a program on fluorinated monomers, i t dibromide and pyrolytic defluorination over silicx-' seemed to us to be of interest to prepare 1,l-difluoro- to yield methacrolein, CH2=C(CH3)CH0. I t may 2 - methylpropene, CF2=C(CH3)2. During the be noted that difluoromethyldimethylcarbinol wr'ls course of this work, we prepared the iso-neric 3,3- not dehydrated by (a! drastic treatment with difluoro-2-methylpropene, CH,=C(CH3)CHF2, the phosphorus pentoxide, (b) the Chugaev reaction, related 3,3-difluoro-3-chloro-2-methylpropene,(c) the boric ester method6 or (d) the Grignard a1CHZ=C(CH~)CF~CI, and the known compounds coholate pyrolysis method.' :
