ssti
JEFFC. D A ~ I JR.. H . ASD KEXNETH S.PITZEI~
7-01, 64
case, although the similarities of the respective [TIS add weight to the assumption that one deals here indeed with B solvents, the difficulties of application of a 0 solvent concept to solutionr of blockpolymers shoidd he clearly recognized. TARLE IV 5%
5
---
--
[v Is--
Type of Methanol [vlgIsodctane blockin " R 3101. u-t. 3101. wt. in "e 3101 a t . w l y m e r solvent" 158,000 15,800 solvent" 1 j8,OOO S p
13; Hi
I
-
133
0
10
20
27 30
(*
12.5 17.0 17.0 24.0 27.0
O.fi5 .OO .63 .. The calculated 6ar drop\ rapidly with increasing temperature and approacheq the region in which :dcohol monomers also are found This behavior of the monomer -hift\ i b itrongly suggestive of nn interaction of the moiionier with the benzene wlvent. It is recognized that molecules with acidic protons a+ociate TTith benzene. and n.m.r. ctudies indicate in swli an association the proton i i drawn into the face of the benzene molecule rather than around the edge.15 I t habeen show1 that the benzene molecule exhibits an anisotropic diamagnetic s eptibility 11-hich can tie xrielved a s arising from a culation of the mobile x electrons around the ring induced by the external magnetic field.Ifi Thege circulating electrons give rise to a qecondary magnetic field around the benzene molecule 'The rnagnitude of this field averaged over all orientationq of the benzene molecule n-ith timr hn- it~eiicalculaterl hy 1-nrioiis means."
-
i
-
I
(17) .I. S. Wailah and R T?i Fessenden J . 4m Chem SOC.,7 9 , 84h C. E. J o h n w n Jr., and P A . Bovey, J . Chem Phiis., 29, 1012 (1958). 11957);
(18) See T. Miyazana a n d IC. S. Pltzer, ibzd information on the trann isomer of formic acid.
30. 1076 (1059), for
July, 1960
K T C L E iR 31-4GNETIC
RESONANCE STCDIES O F HYDROGEN RONDISG
891
TABLEVI association in the aqueous phase, and possible DIMER SHIFTS O F BENZOIC higher polymers. The equilibrium constants obtained by Davies were used to calculate the monoACID IS BEXZENE AFTERADJTSTMENT OF EQUILIBRII-M mer and dimer shifts for acetic acid in benzene at COSSTASTS qeveral temperatures. Daries' values of AH = ( A H = -5.62 kcnl. mole I )
(:A L('Lr1,h'rEL)
?*IOSOMEK A S D
A\,
7'.
=(',
:0i 40
50 60 i0 80 90 100
Kr
2200 1022 1230
955 741 589 468 380
(c.r>.s.f r o n Ijrnzrrit.)
450 4 1:i
388 381 380
;m $24 442
froni lxsnzrnr)
8ir (c.Y.s.
- $25 - 419 -415 - 410 - 40i - 405 - 403 - 400
-8.89 kcal. mole-' and A S = 19.82 cal. deg.-' inole-' were used t o cdculate KSat higher temperatures. The resulting constants and shifts are listed i n Table YII. TABLEVI1 DIVERSHIFTSFOR IN BENZENE ( A H = -8.2 kcal. mole-')
C ~ T , C T - L ~ T E~ \ DI O S O N E R
T , O('.
reported.Iq The I
