which mas previously evacuated and weighed. The flask was then filled with dry ether to precipitate the salt and placed in the refrigerator overnight. The liquor was decanted using an aspirator, but enough was left behind to keep the crystals covered. The remaining liquid was removed under vacuum. The white salt was then dried over phosphorous pentoxide under vacuum. a -P h e n e t h~ ldimethylsulphoniurn bromide-reaction time 96hours; yield 10.17,; 1n.p. 91.7-92.8" C (lit. 1n.p. 76-80" C ref. ( 8 )
N.M.R. STUDIES OF BRIDGED RING SYSTEMS. I. CARBON-HYDROGEN SPIN COUPLING CONSTANTS IN BICYCL0[2,2,1]HEPTANE DERIVATIVES
K. TORI, R. ~I V N E Y U K I , AND H. TANIDAThe carbon-hydrogen spin coupling constants, J C~3 -H , are considered as useful tools for the investigatio~l of s-character of the carbon atomic orbital participating in the C-H bond (1-4). JIuller and Pritchard ( I ) suggested that decrease of the ring size of cycloalkanes with their C-C-C angles increased JC1sPH with the percentage of scharacter of the C-H bond, and, for example, the JC13-H of c>-clopropane exhibited the comparable value to that of the sp2 bond.I t has been known that bicyclo[2,2,l]heptane derivatives have considerably smaller bond angles on their sp3-tetrahedral and spxtrigonal carbons than the respective ordinal angles due to the contribution of ring strain.* llIusher (7) proposed that the unusual behavior of the bicyclo[2,2,l]heptane ring toward the magnetic shielding and the proton coupling constant might be due to the n-character in the ring.
The substituetlt effects on the chemical shifts of the Cg bridge protons in a scries of 6-substituted benzonorbornenes and benzonorbornadienes, and on those of the Cz protons in 6-substituted 2-indanols, were investigated. They were linearly correlated with the modified Hammett relationship 7, -7, = p(um + uP)/2. The p values obtained from the anti-Co protons in the bornenes and bornadienes were slightly but significantly larger than those from the corresponding syn protons, whereas no significant difference was observed between the p values obtained from syn-9-benzonorbornenols and the indanols. The larger pa,,, values were explained in terms of a stereospecific electronic interaction between the T-electron system of the benzene ring and the orbital system of the bridge carbon. In addition, it was shown that the above modified Hammett relationship gives generally a good agreement with the substituent effects on the aliphatic constituents of benzocyclenes and analogous compounds.
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