Synthesis and Properties of Peroxy Oligomers Obtained by Telomerization Effects of the Presence of Bases

<p>New bifunctional oligomers bearing peroxy groups have been synthesized by telomerization in one step reaction. For obtaining oligoperoxides (PO) by telomerization method, epoxide compounds will react with substances containing labile hydrogen atom. Using the principle of stochiometric imbalance between diepoxy compounds and substances with mobile hydrogen atoms and employing a functional peroxide as telogen, the synthesis of PO was studied. 2,2–Di[4–(2,3–epoxy–1-propoxy)phenyl]–propane (diglycidyl ether of diphenylol propane - DGEDPP), 1,2–Di (2,3–epoxy–1-propoxy) ethane (diglycidyl ether of ethylene glycol - DGEEG) and 1,2–Epoxy–3–tert–butylperoxypropane (EP) have been synthesized by methods reported in the literature. Chemical structures have been confirmed by NMR and FTIR, number-average molecular weights M_n of PO_s by cryoscopy, active oxygen content [O]_act. for PO_s was determined by iodometry and epoxy number (<em>e.n</em>.) for PO_s was measured via direct titration of PO samples. A 50% solution of potassium or sodium isopropylates in 2-propanol is used to catalyze the telomerisation. Different parameters such as ratio of components, temperature, reaction time have been optimized in vu to get well defined peroxy oligomers. The presence of peroxy groups in synthesized POs allows us to employ these compounds as curing agents for polymers containing unsaturated double bonds and may be used to improve performance of unsaturated polyester GFR systems.</p>

Alkyne oxidation III. Competitive features and degenerate branching

A comparison is made between the slow com bustions of propyne and butyne-2 which are degenerately branched and acetylene which is not. The relative rates of ‘oxidation’ radical attack on these alkynes and a number of the reactive intermediates formed in their slow combustions have been obtained from their separate and competitive oxidations. The results confirm that the same electrophilic radical species (hydroxyl or hydroperoxyl) is involved in the oxidations of acetylene, propyne and butyne-2. It is concluded that the branching intermediate is a peracid formed from an aldehyde in the case of propyne and an acyl radical in butyne-2 oxidation, which produces only traces of aldehydes, by the sequence: RCHO + X˙→ RĊO + HX ; RĊO + O 2 → RCO˙ 3 ; RCO˙ 3 + RʹH→ RCO 3 H + Rʹ˙ ; RCO 3 H → R˙ + CO 2 +˙OH, where X˙ is a chain carrier and RʹH a molecule with a labile hydrogen atom. In acetylene oxidation the hydrogen abstraction reaction is too slow to compete with alternative reactions of the acyl radical and hence it is not branched.

The Interaction of Tetramethylthiuram Disulfide with Rubber and with Compounds Containing a Labile Hydrogen Atom

In the interaction of TMTD with rubber, sulfur and nitrogen from the TMTD add to the rubber, a maximum being exhibited on the rate curve for sulfur addition. At the same time dimethyldithiocarbamic acid is formed which, in mixtures containing zinc oxide, becomes bound in the form of Zn-DDC but which decomposes to carbon disulfide and dimethylamine in mixtures containing magnesium and calcium oxides and in the absence of metallic oxides. In the absence of oxides or in the presence of CaO or MgO a less dense three dimensional network is formed and reversion takes place which is accelerated by carbon disulfide and dimethylamine. The degree of crosslinking increases with increase in content of 1,4 structural units while the amount of combined sulfur and the rate of accumulation of zinc dithiocarbamate diminish. Dithiocarbamic acid also forms in the interaction of TMTD with geraniol and isopropylbenzene. The thermal decomposition of TMTD to thiuram monosulfide, sulfur, tetramethylthiourea and carbon disulfide takes place in the absence of compounds with a labile hydrogen atom. The reaction proceeds through the stage of rupture of the S—S and C—;S bonds of TMTD to form free radicals. The radical mechanism of the reaction is confirmed by electronic paramagnetic resonance specta.