Title: ISOMERIZATION OF STILBENES (thesis)

Abstract

The following cis and trans stilbenes were syrthesized: stilbene, p- chlorostilbene, p-nitroatllbene, alltrans azoxystilbene, cis-trans-cis azoxystilbene, p-aminostilbene, p-N-acetyl-aininostilbene. Decarboxylation of p- hydroxy-and p-acetoxy-1-carboxy stilbene were studied and in all cases only the trans isomer were obtained. The following cis stilbene derivatives were prepared by irradiation of the trans derivatives: stilbene, p-hydroxystilbene, p-ac etoxystilbene, p-aininostilbene, cis-trans-cis and all-cis azoxystilbene. The latter two compounds are extremely unstable and isomerize during puriflcation. The reaction rates were obtained from experiments planned primarily to obtain optimum conditions for the preparation of new stilbene derivatives. hates of trans-cis isomerization at 50 deg C were obtained for: stilbene-k 1.8, 10/sup -4/ sec/sup -1/ in benzene solution p-acetoxystilbene-1.2 x 10/sup -4/ sec/sup -1/ in benzene, p-hydroxystilbene-2.0 x 10/sup -4/ sec/sup ->/ in ethanol, p- aininostilbene-9.8 x 10/sup -4/ sec/sup -1/ in 50% ethaml-2 N HCl. Rate constants for thermal, that is, cis-trans isomerization were evaluated for trans- cistrans azoxystilbene. Its rate constant at O deg C in 10% benzene n-hexane is 6.9% 10/sup -5/ sec/sup -1/. Therefore no pure trans-cis-trans azoxystilbene could be isolated. The thermal isomerization of cis aininostilbene in 2 n hydrochloric acid-50% athanol was studied at 40 and 80 deg C. The energy of activationmore » was 15.5 kcal/mole. At 50 deg the rate constant of cis-trans isomerization is then k = 4.2 10/sup -5/ sec/sup -1/. From the rate constant for the reverse reaction an equilibrium constant of K = k trans-cis/ k cis -trans = 23 is calculated and thus trans-aminostilbene as the cation can be isomerized under the influence of ultra violet light to the extent of 96%, although the actual yield must undoubtedly be smaller due to secondary reactions. The pK of cis and trans p-aminostilbene was measured in 30% methanol citrate buffer. It is found that the two isomers have, within experimental error, identical pK values of 4.10 at 25 deg C. Hammett's substituent constant is therefore of the onder of epsilon = 0.06. Under certain conditions, it seems possible to diazotize cis aminostilbene to yield cis stilbenediazonium salts. The spectra of both the cis ard trans diazonium ion were measured as well as their coupling product with H- acid. There is good evidence that the reduction of cis stilbene-diazonium ion with hypophosphorous acid yields mainly cis stilbene. Systematic collation of the spectra of the monosubstituted stilbenes prepared, for both the cis and trans isomer, were made and the results compared with analogs in the benzene series. In addition infrared spectra were measured. The cis derivatives show a sharp characteristic absorption band at 615-920 wave numbers. For the transderivatives a characteristic absorption band is found at 957-968 wave numbers. (auth)« less

Authors:

Schmid, P.

Publication Date:

Tue Sep 01 00:00:00 EDT 1959

Research Org.:

California Univ., Berkeley, CA (US). Lawrence Radiation Lab.

OSTI Identifier:

4199031

Report Number(s):

UCRL-8883

NSA Number:

NSA-14-000096

DOE Contract Number:

W-7405-ENG-48

Resource Type:

Technical Report

Resource Relation:

Other Information: Orig. Receipt Date: 31-DEC-60

Country of Publication:

United States

Language:

English

Subject:

CHEMISTRY; ABSORPTION; ACETYL RADICALS; AMINES; AROMATICS; BENZENE; CHLORINATED HYDROCARBONS; CITRIC ACID; ETHANOL; HEXANE; HYDROCHLORIC ACID; INFRARED RADIATION; IRRADIATION; ISOMERS; LIGHT; MEASURED VALUES; METHANOL; ORGANIC NITROGEN COMPOUNDS; PHENYL RADICALS; PREPARATION; SOLUTIONS; SPECTRA; STILBENE; ULTRAVIOLET RADIATION