OCTOBER
1959
1577
NOTES
environmental factors were responsible for initiation of the allylic bromination of the secondary allylic hydrogen in cyclohexene by NBS under the original Ziegler reaction conditions. HYPJ. DAUBEN, JR., AND LAYTON L. hfcCo~a Ethyl 4-methyl-2-pentenoate when freshly distilled gives a negative test for peroxides but perReceived April 6, 1969 oxidic impurities are formed, presumably by In a number of textbooks and reference books autoxidation, when this material is allowed t o on organic chemistry it is stated that allylic bromi- stand in a glass-stoppered bottle. Under the ordinations of tertiary hydrogens by NBS is not pos- nary conditions (refluxing parbon tetrachloride, sible under Ziegler’s original conditions (in re- diffuse laboratory light, air access through top of fluxing carbon tetrachloride without irradiation or condenser) stale ethyl Pmethyl-Zpentenoate readdition of initiators) but may be effected when acts completely with NBS in
