high concentration (0.1M) of sodium sulfate, Dr. Morris says. The sodium sulfate prevents emulsification and promotes rapid phase separation. The titration is reliable for fluoride concentrations from 1 Χ 10 - 3 to 50 X 10" 3 M, the two Penn State chemists find. It's necessary, how ever, to remove halide, nitrate, nitrite, sulfite, and thiocyanate ions before the extraction, they point out. If these ions aren't removed, they are ex tracted along with fluoride, and posi tive end-point errors and small titra tion curve slopes at the end point are obtained. The Penn State pair has thus devel oped a simple, rapid fluoride titration by taking advantage of the extraction chemistry of organometallic com pounds. They point out that the prob lem of nitrate interference can be solved if the ion is removed by ex tracting it with tetraphenylarsonium ion, which does not extract fluoride. The extraction properties of tetraphenylphosphonium salts are quite similar to those of the corresponding tetraphenylarsonium salts, but quite different from those of the antimony salts. Tetraphenylphosphonium sul fate could have been used to remove nitrate, but it is more expensive and a little less efficient than the arsonium sulfate, he explains. Tetraphenylarsonium cation seems to be a good extractive titrant for chlorate, perchlorate, or nitrate, Dr. Morris finds. He and Mr. Orenberg are beginning to study the titrations of these anions. Certain organometallic cations of nontransition metals—generally of the R n M+ type—form precipitates with various ions. Thus these cations can be used as selective titrants for certain anions. For example, tetraphenylar sonium chloride has been used recently for the analysis of hexafluorophosphate and other complex anions. And tetraphenylantimony sulfate is useful as a titrant for perchlorate, perrhenate, and pertechnate. Most organometallic cations are polarographically reducible. Amperometry with the dropping mercury elec trode therefore can be a convenient way to detect the end point in titra tions with these reagents, Dr. Morris points out. For example, he and Mr. Orenberg have followed the titration of perchlorate with tetraphenylantimony sulfate amperometrically. Dr. Morris and Joseph DiGregorio, another Penn State graduate student, are currently studying amperometric titrations of nitrate with diphenylthallium fluoride. The availability of ni trate-sensitive electrodes makes potentiometric titration of nitrate with diarylthallium cations an attractive pos sibility, Dr. Morris says. 42 C&EN JULY 10, 1967
Lithium salt leads to stable epoxyamine that shows unexpected ring expansion Chemists at Wayne State University, Detroit, Mich., have successfully iso lated and characterized epoxyamines, a new class of chemical compounds. The concept of the epoxyamine func tional group had been previously pro posed, but scientists have thought compounds containing it occur mainly as intermediates in other chemical re actions. Now, however, Dr. Calvin L. Ste vens of WSU's chemistry department and his coworkers, P. Madhavan Pillai and T. R. Potts, have synthesized a stable, crystalline, epoxyamine, 2 - ( l aziridinyl) - 2 -phenyl-l-oxaspiro[2.5]octane [/. Am. Chem. Soc, 89, 3084 (1967)]. The synthesis route used will probably lead to a generalized re action scheme, Dr. Stevens points out. Dimethyl and cyclopentyl analogs have been prepared, although charac terization studies on these materials have not been published. The apparent inaccessibility of this class of compounds was thought to be due to high reactivity of the epoxy amine group and its tendency to rear range. Epoxyamines rearrange read ily, but in a way contrary to that which would normally be expected, the WSU workers find. For example, the epoxyamines isomerize to aminoketones. In the Wayne experiments, the pro totype material was prepared by react ing a-bromocyclohexyl phenyl ketone with the lithium salt of ethylenimine in ether at room temperature. The product was isolated by distillation
and purified by recrystallization from pentane. The corresponding epoxy amine, formed in 7 5 % yield, had a boiling point of 90° to 95° C. and a melting point of 20° to 22° C. The in frared spectrum shows no hydroxyl or carbonyl absorptions, but has strong peaks at 1025 and 1045 cm.- 1 The nuclear magnetic resonance spectrum is consistent with the epoxyamine structure, showing aromatic protons from τ = 2.45 to 2.85 and aliphatic protons from τ = 7.8 to 9.0 in a 5:14 ratio. Some of the reactions of the epoxy amine compound furnish added confir mation of the structure and, at the same time, point to the versatility of epoxyamine as a functional group. For example, acid hydrolysis of the compound converts it quantitatively to the known ketone, a-hydroxycyclohexyl phenyl ketone. Reduction with sodium borohydride in methanol gives [ 1-a- ( 1-aziridinyl ) benzyl] cyclohexanol, whose hydrogénation yields (l-a:-N-ethylaminobenzyl)cyclohexanol. This amino alcohol can also be obtained by direct hydrogénation of the epoxyamine. Of particular interest is the rearrangement which the epoxyamine undergoes. When refluxed in o-dichlorobenzene, the rearrangement with ring expansion occurs to give 2-(1-aziridinyl ) -2-phenylcycloheptanone. According to previous ideas on epoxyamine rearrangements, a- ( 1-aziridinyl) cyclohexyl phenyl ketone would have been the product.
α-Bromoketone gives rise to the new epoxyamine which rearranges to form a seven-membered ring
