TABLE1 V SouIKJM METHOXIDE I?? h/lb.THANUI,
l < I N U T I C COSSTANTS FUR R E A C T I O N S IYITII
A H *, kcal.
lOjk (I.mole-' sec.-ll 30°
20 30
Halide
a.5 +, e.u.
-3.2 i9 433 f 9 20.8 f 0 , 4 14.9 f 0 . 2 CHJI 24.4 f 0.7 -3 1 i2 4.41 f 0.16 0 , 0 8 6 3 f . oo4 CICH2I 2 1 . 0 i 1.0 - 1 I . i i 'I ,031 f ,f)o:3'L i . 0 2 f .IU BrCHJ L't.7 i2.0 -G,4 zk i 0.536 f . l K i S .oio ,1102~ 1CH.I" -5.9 i 2 472 zt 24 20.5 f 0.7 17.1 f .6 CHaBr 29.0 f 0 . 0 -5.9 f 2 L 3 3 i .w -17.2 f 1 . 6 CHaCHpBr I'CI-I.Br i , 3 i f ,14 22; i 11 21.1 f 0 . 7 -,j,ti 2 C1C H R r " O,O-~lSi .OOl 2 ,:;e f (1 I):I 9t?,fJf 11.4. -2,,j i2 BrCH.Br",' il.00616 f .0005 0.3iO f ,02 25.4 f0.7 -4.9 Z t 2 ClCHZC1" 0 ,0284 i- ,001 ' k 'l'lie o1)icrvctl r a t e coiiitatiti have bcen tiivitlctl by L ~ V O to gct the r a t e c o i i ~ t a i i t spcr iotlitlc ( I N I I C P l>rolltiilc or chloritic) Estirnatcci by cxlrspolatioii tu zcro titnc. diotvn. .4t Xi", IOjk = O X 8 f 0.002. I: At 36", lVk = 0.0613 f O.(JO2.
+
tivc conipounds during the several weeks rcquired for a kinetic run a t this temperature. The values given in Table I V were therefore obtained by extrapolation to zero time.
Discussion I t is seer1 that as a-substituents all four halogens (compared to hydrogen) decrease the reactivity by the SN:! mechanism in both of the reactions studied. This decrease in reactivity is least for fluorine where it is in one case less and in the other case somewhat more than that produced by a methyl group. The decrease is more for chlorine and most for iodine and bromine. I n a number of cases the diffcrences in heats of activation clearly contribute to the differences in reactivity. In most cases the differences in entropies of actibation
[ C O N T R I H U T I O N IiKOM L ) E P h R I ' M E N T OF
are no larger than our sometimes coiisiderahlc experimental error, Therefore in few cases can we be sure that an entropy difference contributes to the difference in reactivity. The data nresented herein will be discussed firther in a subsequent, more general article on the effcct ol structure 011 SN:! reactivity, Acknowledgments.-The authors would like to express their gratitude to the Research Corporation of New York for the grant of a fellowship to C. H. T. and to the National Science Foundation for a fellowship to S. J. E., and for other support which has made this work possible; and to the Dow Chemical Company for samples of methylene bromide and bromochloromethane. ATI.AATA, GE~R2 60 - 1 l h (calcd.) 74.69, (foulid] 73.40. I
Carbon
1ZZ0D
Allyl ether
~ I K (calcd.) D 59.81, (found) 61.73.
'I
.\iKu
butyl a t the a-position in n-butyl l-n-butyl-3methylallyl ether or the t-butyl group in t-butyl 1f-butyl-3-methylallyl ether does not prevent 12addition of phenylmagnesium bromide. Seemingly structural variation of the ether in the y- or a- and y-positions has no effect upon the mode of cleavage by the Grignard reagent when the reagent is aryl or alkyl (lower than n-heptyl). The minimum structural alteration of the ether required for a change in the mode of cleavage by n-heptyl- and n-octylmagnesium bromides is replacement of one y-hydrogen by a methyl or phenyl group. In general the yields of the olefinic hydrocarbon products were higher from reactions involving disubstituted allyl ethers and Grignard reagents than from monosubstituted ethers. A11 experiments were carried out in an excess of Grignard reagent over unsaturated ether and a t the refluxing temperature of diethyl ether or benzene used as solvents. Because of the possibility of allylic rearrangement, it was necessary to establish the structure of the substituted ethers used in this investigation. The products obtained from ozonization studies indicated that the ethers had riot undergone rearrangemen t . Acknowledgment.--The authors thank Professor D. C. Gandy for assistance in the analysis of the allyl ethers and nitrogen compounds.
Experimentalj Synthesis of Substituted Allyl Ethers.--The allyl ethers used in this investigation were synthesized in acceptable yields by two general methods.6-8 The phenethJr1-, phenethyl 3-phenyl- and n-butyl 3-phenylallyl ethers were synthesized bl- condensation of appropriate sodium alkoxides aud alkl-1 halides. The n-butyl l-n-butyl-3-rnethyl-, n butyl 1-benzyl-3-phenyl- and t-butyl 1-t-butyl-3-methylallyl ethers were synthesized by treatment of appropriate aldehydes with suitable Grignard reagents followed b?. condensation of the resulting secondary alcohols, through their sodium oxides, with the required alkyl halides. Physical constants and analytical data of the new allyl ethers are shown in Table I. Determination of Structures of Substituted Allyl Ethers.Three to five-g. samples of phenethyl 3-phenyl-, n-butyl 3phenyl-, n-butyl l-n-butvl-:~-methvl-, t-butyl l-t-butyl-3methyl- and n-butyl I -benzyl-3-phenylallyl ethers were disf 5 j h l e l t i n y points aril corrected. ili)
E. A . Tallry. A . S.Hiinter a n d IC. I-anoviky, T H I SJ o I I K N A I . , 73,
%i28 (1951). ( 7 ) S. 1'. X I u l l l k e n . I
