FLUORINATED ,\ROMATIC VINYLCOMPOUNDS
July, 1946
2. This method which allows both for the variation of the alkyl and the aryl groups gives
[CONTRIBUTION FROM
THE
i 139
mixtures of isomers in all cases tried thus far. IOWA CITY, I O W A
KECI.:IVED DECI~MRPR 12, 1945
CENTRAL RESEARCH DEPARTMENT, MONSANTO CHEMICAL C~MPAN 1 Y
Vinyl Aromatic Compounds. 111. Fluorinated Derivatives' BY MARYW. KENOLL~" .4s part of a study on substituted styrenes, vinyl derivatives of fluorinated benzene, toluene and biphenyl have been prepared, with the fluorine located in the benzene ring or in a methyl side chain. In all cases a fluorinated hydrocarbon was the starting point of the syntheses and the problem was thus one of introducing the vinyl substituent. When the fluorine atom is in the ring the fluorinated hydrocarbon can be subjected to acetylation with acetic anhydride in presence of aluminum chloride, without loss of fluorine. This yields a methyl aryl ketone which can be reduced tc a secondary carbinol; dehydration of the latter yields the desired vinyl compound. p-Fluorostyrene and 2-fluoro-4'-vinylbiphenyl were prepared in this way according to the following series of reactions :
-----f
CF3C---
,CH--C H z l:;$\l
determination. In 2-fluorobipheny1, Ltcetylatioii could affect the fluorinated ring but this was C'I 11:considered improbable sirice the c!rtho-p;ir;i-di recting influence of the fluorine aturn woul:l be hindered by the phenyl group and reactiim ~rc~iilti be slower than in an unsubstituted ring. ,Ilso, it is known that nitration of 2-fluorobiphenyl4 gi\-es only traces of 3-fuuro-Cnitrobiphen!.l, t lir n i i n products being "-~uoro--l'-Iiitrohiplien!l a i i d 2fluoro-t"-ni trobiphenyl. Oxidation oi L'-tlurfruhi. phenyl methyl ketone gave a fluorobi],hcii>~l ex__ bosylic acid. To establish the striicturt-~ltlinltc-l!, F-c> --+F \ - - COCH? + the ketone wa6 hyclrugeiiatrd under mlitioiis --+ F /\- CH==CH~ which w:mld simu1t:tric:ously cliniiiiii tc fliloriiic hydrogen fluoride, anti satuixtt, t'lic :irq.mi:itic. (1) ring.6 The p - c ~ - ~ , l c ) h e s v l e t l i \ , l ~f ~~J tl ~i n~i c< 'iI-> (~ \,!L' ~ F found to he identicxi with a s i r n ; i l c o l ~ ~ c i i i IJ:: i ~ d + COCH, +- the reduction o f y-i)hen~lacetiii~l-i;i hydrogenation l i d affected the hr1i-i F which WRS non-acetylated was coritir~inctib y tion to terephthalic acid. It \vas thu.; p r ~ \ e d < ~ O - C H O H C H J --+ that the introduction (if the acet) 1 gr"njJ in 2fluorobiphenyl has taken place in the p u t position of the non-fluorinated ring. The molecular reiractions, JIRI), were c,;lc:ulated by means of the Lorentz-Lorertz i, ~niu1.1. When the fluorine is present i n a methyl side chain, as in benzotrifluoride, the above procedure The atomic refraction for fluorine, -1Ri;, \v: cannot be used because of the halogen exchange tained by subtracting froni the niolrcul~irr which occurs between the organic fluoride and tion the increments for C(t'.41Sj, l l j l aluminum chloride.2 I t is, however,. possible to Br(8.865), benzene ring (5.199), and O(carhony1 introduce a bromine atom in a position rneta to 2.211 or hydroxyl 1.523). The exaltation, E M the trifluoromethyl group, transform the bromide for MRD +1.17, for styrene was applied as a into a Grignard reagent3 and condense the latter correction in calculating A R F fur p-fluorostyrerw with acetaldehyde. This series of reactions gives a and m-trifluorornethylstyrene. A similar correcmethyl aryl carbinol which by dehydration yields tion, EM for MRD +0.7S, for acetophenone the desired vinyl compound, rn-trifluoromethyl- was applied in the case of p-fluoroacetophenone. The theoretical values used are those reported by styrene. Only in series (2) is there a problem of structure Eisenlohr.6 All the compounds studied show values for ARF in line with those found in aliphatic (1) The preceding paper of this series, Huber, Renoll, Rossow and compounds. Mowry, THISJ O U R N A L , 68, 1109 (1946) -(,
>
F-O-CHOHCH? >
