Chain‐Length‐Dependent Termination of Vinyl Acetate and Vinyl Pivalate Bulk Homopolymerizations Studied by SP‐PLP‐EPR

Bulk homopolymerizations of vinyl acetate and vinyl pivalate are studied by EPR experiments between ?65 °C and 60 °C with dicumyl peroxide acting as the photoinitiator. No mid‐chain radicals are seen, which demonstrates that backbiting plays no role. The chain‐length dependence of the termination rate coefficients measured up to 13% monomer conversion is adequately represented by the composite model. The power‐law exponents α_s and α_l for short‐chain and long‐chain radicals are: α_s(VAc) = 0.57 ± 0.05, α_s(VPi) = 0.67 ± 0.15, α_l(VAc) = 0.16 ± 0.07, and α_l(VPi) = 0.16 ± 0.07. The crossover chain lengths differ largely: i_c(VAc) = 20 ± 10 and i_c(VPi) = 110 ± 30. The rate coefficient for termination of two radicals of chain length unity, , which is the fourth composite‐model parameter, depends on temperature, as does the monomer fluidity.

     

Corticosteroid cross-reactions: an alternative view

An alternative view of corticosteroid cross-reactivity is proposed, based on 2 immune recognition sites on the corticosteroid molecule, 1 influenced by C 6/9 substitution and 1 by C 16/17 substitution. A case report is adduced in support of such a hypothesis.     

Contact allergy to hydrocortisone and thixocortol pivalate: problems in the detection of corticosteroid sensitivity

Several of the difficulties involved in the detection of corticosteroid allergy are illustrated by the problems encountered in a patient sensitive to a preparation containing hydrocortisone and miconazole nitrate. The importance of appropriate concentrations and vehicles for patch testing, the possible role of impurities, and cross-sensitivity of corticosteroid molecules are discussed.     

Corticosteroid allergy

Allergy to corticosteroids is becoming increasingly recognized. Diagnosis is difficult because of frequently false-negative patch tests. The optimum concentration and vehicle for patch testing with pure corticosteroid has still not been established. The patch test results of 19 patients with allergy to corticosteroids seen at the Skin and Cancer Foundation in Sydney, Australia, were analysed. It was found that patch testing with the patient's corticosteroid in the commercial cream base gave a greater yield of positive results than testing with the commercial corticosteroid ointment or with the pure corticosteroid in either petrolatum or in alcohol. Tixocortol pivalate, and lo a lesser extent budesonide, were useful for detecting allergy to hydrocortisone, but not necessarily other corticosteroids. Delayed positive patch tests were often seen, showing the importance of carrying out a late reading. The repeal open application test (ROAT) with the patient's own corticosteroid was found lo be a simple, useful diagnostic test.     

Sensitization studies with mometasone furoate, tixocortol pivalate, and budesonide in the guinea pig

Mometasone furoate is a new corticosteroid, synthesized to have an improved ratio of anti-inflammatory potential to adverse effects. The guinea pig maximization test was used to determine the sensitizing capacity of mometasone furoate, and also to investigate cross-reaction patterns in animals sensitized to tixocortol pivalate and budesonide, respectively. Tixocortol pivalate was shown to be a sensitizer in the guinea pig, but cross-reactions to other tested corticosteroids wore not observed. Furthermore, no sensitizing capacity could be demonstrated for budesonide or mometasone furoate.     

特戊酸氯甲酯合成新工艺的研究

目的 探讨合成特戊酸氯甲酯的简便工艺方法。方法 以己内酰胺作催化剂，特戊酸和氯化亚砜室温反应得到特戊酰氯，不经分离，补加适量氯化亚砜后直接与氯化锌和多聚甲醛室温反应合成特戊酸氯甲酯。结果 特戊酸氯甲酯总收率94．2％，产品结构经TR，1H NMR确认。结论 该法一步完成，条件温和，操作简单，值得进一步进行工业化开发。