Epoxides titration

Several solvent systems have been utilized for epoxide titration. Desirable properties for a solvent in this connexion are 1 that it be easy to purify and store (2) that it be unreactivc towards both tin-epoxide and the epoxide reagent and 3 that it not be excessively volatile, noxious, or toxic. 

Aqueous epoxide titration suffers from two serious defect. Tki-first is the limited solubility of many epoxidea in water, a handicap sometimes overcome by replacement of water by ethanol. The second is the competing aoid-catalyzed hydrolysis, equally troublesome in ethanol since ethanolysis constitutes a side-reaction as much n docs hydrolysis. Partial suppression of these interfering processes is achieved at high halide concentration, as reported for example by Deokert. v-msi Kerckow, Lubatti.1440 and others,8. 47 804... 

Anhydrous epoxide titrations have been conducted in a variety of organio solvents. EtbercaJ hydrogen chloride, for example, has Ixcn u in several laboratories, but is not alwavi ... 

Various well-established procedures have been reviewed Some of them have been used for epoxide titration in epoxy-carboxy kinetic studies ... 

Procedures. The equivalent weight of DGEBA was determined to be 172.1, by titrating epoxide groups using the hydrogen brceiide/acetic acid method (9). 

Epoxidaiion of HPL. Results from the epoxidation of HPL with ECH in the presence of KOH and QAS using methylene chloride (at room temperature) as solvent are shown in Figure 3. The degree of conversion of (aliphatic) hydroxy groups of HPL to epoxide functionality was monitored by titration. Parameters important to the success of this reaction included (a) stepwise addition of KOH, approximately paralleling the formation of KC1 by dechlorohydrogenation (b) presence of QAS in the reaction mixture (c) an at least five-fold stoichiometric excess of ECH over available... 

Epoxyoctane. A solution of 1 gram of f erf-butyl hydroperoxide (97% purity), 3 ml. of octene-1, 3 ml. of benzene, and 0.005 gram of molybdenum hexacarbonyl was sealed in a pressure tube and allowed to react for 1 hr. in a constant temperature bath at 90°C. The tube was removed and cooled in ice water. Hydroperoxide and epoxide were analyzed by iodometric titration and GLC. There was a 75% conversion of the hydroperoxide and a 92% yield of the epoxide based on the hydroperoxide conversion. 

With very few exceptions, quantitative epoxide assay techniques currently in use are derived from the reeotion of ethylene oxides with halogen adds, notably hydrochloric acid and hydrobromio add, in a variety of solvents. Acid uptake may be determined by any of several reliable procedures. These include titration with standard base8 nr back-titration with standard acid.744 The end-point may be detected visually in the presence of suitable acid-base indicators, or by the more precise technique of potontionaetry.447.4 -470 A useful alternative, applicable in the presence of easily hydrolysed substances or of amines that buffer the end-point, is the technique of argentiometry. In this procedure excess of halide ion is titrated with silver nitrate in tV presence of ferric thiocyanate indicator,470 1884 or potentiometri-cally.188 ... 

Several analytical procedures are baaed on the hydration rather than hydrohalogenation of epoxide . Tlie resultittg 1,2-diols are assayed by oxidative titration with periodic acid in aqueous sulfurio acid or perchloric acid.4711 Alternatively, carbonyl compounds formed on periodic acid oxidation of 1,2-diola may be determined color imetricajlv wkh phenylbydrwine or other suitable reagents.247 374... 

Addition of certain sulfur-containing nucleophiles constitutes the basis of several analytical procedures. Among these nucleophiles arc Rodium sulfite,1 75 sodium thiosulfate,1491 and hydrogen sulfide.635 In each case, OH ions released after attack of the nucleophile on the epoxide can be titrated continuously with standard acid to maintain a constant pH.1491... 

Styrene oxide and certain di- and trisubstituted epoxides cannot be assayed satisfactorily by titration with arid on account of their tendency to undergo isomerization to carbonyl compounds. 

Gascon and co-workers developed an analytical method suitable for the determination of 1,2-epoxy-2,4,4-trimethylpentane.<2D The epoxide was heated at 100° in a sealed tube with di-n-butylamine, and the resulting product aoetylated with acetic anhydride. Titration with perchloric arid in aoetie acid containing a suitable indicator gave the amount of tertiary amine formed. 

This article shows how successfully the cascade branching theory works for systems of practical interest. It is a main feature of the Flory-Stockmayer and the cascade theory that all mentioned properties of the branched system are exhaustively described by the probabilities which describe how many links of defined type have been formed on some repeating unit. These link probabilities are very directly related to the extent of reaction which can be obtained either by titration (e.g. of the phenolic OH and the epoxide groups in epoxide resins based on bisphenol A206,207)), or from kinetic quantities (e.g. the chain transfer constant and monomer conversion106,107,116)). The time dependence is fully included in these link probabilities and does not appear explicitly in the final equations for the measurable quantities. 

In concomitance with the displacement observed by i.r., an evolution of the catalytic activity has been observed while studying the liquid-phase epoxidation of cyclohexene in the presence of (EGDA)- Mo(VI), freshly prepared or after four months of conditioning at room temperature under inert atmosphere. As usual, the appearance of epoxide was followed by gas chromatographic analyses or by direct titration of oxirane oxygen and the disappearance of hydroperoxide was monitored by iodometric titration. In figure we report concentration-time for typical runs in ethylbenzene at 80°C obtained with the experimental procedure already described (ref. 9). It may be seen that with a freshly prepared catalyst an induction period is observed which lowers the initial catalytic activity. Our modified Michaelis-Menten type model equation (ref. 9) cannot adequately fit the kinetic curves obtained due to the absence of kinetic parameters which account for the apparent initial induction period (see Figure). 

Reed 332) has reported that reaction of ethylene oxide with the a,(a-dilithiumpoly-butadiene in predominantly hydrocarbon media (some residual ether from the dilithium initiator preparation was present) produced telechelic polybutadienes with hydroxyl functionalities (determined by infrared spectroscopy) of 2.0 + 0.1 in most cases. A recent report by Morton, et al.146) confirms the efficiency of the ethylene oxide termination reaction for a,ta-dilithiumpolyisoprene functionalities of 1.99, 1.92 and 2.0j were reported (determined by titration using Method B of ASTM method E222-66). It should be noted, however, that term of a, co-dilithium-polymers with ethylene oxide resulted in gel formation which required 1-4 days for completion. In general, epoxides are not polymerized by lithium bases 333,334), presumably because of the unreactivity of the strongly associated lithium alkoxides641 which are formed. With counter ions such as sodium or potassium, reaction of the polymeric anions with ethylene oxide will effect polymerization to form block copolymers (Eq. (80) 334 336>). 

Cyclodextrins have been covalently modified for catalytic oxidation, such as compounds 57, 62-65 (Schemes 3.14 to 3.16) [44, 45]. Enantioselective epoxidation of styrene derivatives, and carene using 20-100 mol% of the CD-ketoester 57 has been achieved. The inclusion-complex formation was confirmed by aH NMR titration experiments, confirming the 1 1 substrate catalyst stoichiometry under the reaction conditions. In the oxidation of carene, NOE and ROESY experiments showed different behavior according to the size of the R group (Scheme 13.14). Evidence was found for the formation of inclusion complexes with compounds 58 and 59. On the other hand, compounds 60 and 61 proved to interact with the catalyst via a tail inclusion vide infra). The increased diastereoselectivity observed with compounds 58 and 59 might be explained by a closer proximity to the covalently linked dioxirane. 

Fig. 8. Dependence of the fraction of tertiary amine groups in the systems dodecylamine (DDA)-phenyl glycidyl ether (PGE), DDA-DGEBA, and HMD-DGEBA on conversion of amine functionalities. GPC determination DDA-PGE determination of Up and a, by titration HMD-DGEBA epoxide in excess . amine in excess O DDA-DGEBA amine in excess . The curve was calculated for e = 0,41...

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