Neopentyl structure

Oxidative Stability of Carboxylated Polyesters. The polyesters which were extended with dianhydrides are those in Table I which were soluble in the lacquer solvents. Of these, theoretical considerations indicate that T50I(NPG) should be the most oxidatively and thermally stable because it is the only one with a completely aromatic acid component (terephthalic and isophthalic), and the glycol component has the stable neopentyl structure. When K-l polycarbonate films containing 5% of this polyester extended with PMDA were heated in a forced-air oven at 200°C, the film life (time to brittleness when creased) was not lowered appreciably (compared with a control containing no carboxylated polyester). The incorporation of 5% of the similar carboxylated T50H(NPG)... 

Synthetic esters like polyol esters or neopentyl polyol esters are made from monobasic fatty acids and polyhedric alcohols with a neopentyl structure (see Figure 7.6). On these molecules, there are no hydrogen atoms on the beta carbon. This carbon is where thermal attack occurs on diesters and eliminating it improves the thermal stability of the molecule. Polyol esters have an increased number of ester groups versus diesters. This feature increases polarity, which will affect the lubricity of the oil at elevated temperatures and give it an advantage over PAOs. 

The lack of benefit from the neopentyl structure. Polymer II,... 

The neopentyl structure increases thermal stability, so that this compound is useful as a flame-retardant additive in extruded polymethyl methacrylate sheet. 

Efforts to find conditions where the formyl group will be attached to a branched carbon atom have met with only limited success. With isobutylene at higher temperature (220 °C) and pressure (425 atm) required for catalyst stability, an 8% yield of neopentyl compounds is obtained, together with 61.6% yield of isopentyl compounds. At the same time, 25% of the starting material was hydrogenated [237]. Good yields of the neopentyl structures have been obtained only at room temperature with stoichiometric quantities of hydrocarbonyl [35] (see also p. 9). 

Dimethyl-3,4-dipropoxythiophene (ProDOT-Me2) has further increased properties in several respects, but an alternative synthetic strategy had been necessary compared to ProDOT. The synthesis of ProDOT-Me2 was first published in 1999.11 In the same publication, ProDOT synthesis was performed in the manner described before by Williamson ether synthesis with 1,3- dibro-mopropane and 3,4-dihydrox5 iopene-2,5-diethylcarboxylate and subsequent ester hydrolysis and decarboxylation.i For the preparation of the new ProDOT-Me, in principle the same procedure has been used, utilizing 2-methylpropane-l,3-ditosylate instead of the 1,3-dibromide.n In contrast to the less substituted ProDOT or ProDOT-Me, Williamson ether synthesis with neopentylbromide or similar compounds was not sufficient for ProDOT-Me2— not unexpected for a neopentyl structure. So acid catalyzed... 

The extent to which rearrangement occurs depends on the structure of the cation and foe nature of the reaction medium. Capture of carbocations by nucleophiles is a process with a very low activation energy, so that only very fast rearrangements can occur in the presence of nucleophiles. Neopentyl systems, for example, often react to give r-pentyl products. This is very likely to occur under solvolytic conditions but can be avoided by adjusting reaction conditions to favor direct substitution, for example, by use of an aptotic dipolar solvent to enhance the reactivity of the nucleophile. In contrast, in nonnucleophilic media, in which fhe carbocations have a longer lifetime, several successive rearrangement steps may occur. This accounts for the fact that the most stable possible ion is usually the one observed in superacid systems. 

Very active catalysts for the preparation of strictly alternating butadiene-propylene copolymers (BPR) consist of V0(0R)2C1/i-Bu Al (R = neopentyl). The CH3 side groups in BPR stiffen the polymer chain and were expected to promote the formation of strain-induced structures. The fact that we could not detect strain-induced crystallization is probably due to an atactic configuration of the propylene units. 

Henrick, K., Hudson, H.R., and Kow, A., Michaelis-Arbuzov intermediates x-ray crystal structures of the methyl bromide adducts of neopentyl diphe-nylphosphinite and dineopentyl phenylphosphonite, Chem. Commun., 226, 1980. 

The reduction of di(neopentyl)gallium chloride with lithium naphthalide was reported to afford the gallium clusters (Ga-CH2CMe3) , but their structures are hitherto unknown. It was assumed that different species with up to 12 gallium... 

Pr, -Bu, Me3SiCH2, neopentyl, 4-F-CeH4, 2-MeO-CeH4 Scheme 8.22. Investigation of substrate and Grignard reagent structure. 

Bis(neopentyl)magnesium (47) occurs in benzene solution as a trimer, for which both a linear structure I and a cyclic structure II (Figure 28) have been proposed. ... 

The structure of cyclopentadienyl(neopentyl)magnesium (65) in the gas phase has been determined by gas-phase electron diffraction . The Mg—C bond distances of the rf-bonded cyclopentadienyl group are 2.328(7) A while the Mg—C bond distance of the neopentyl group was found to be 2.12(2) A. 

In an approach similar to the synthesis of 12, the neopentyl derivatives [(Me3CCH2)3Zn] K(C6H6) (17) and [(Me3CCH2)3Zn]Na (18) have been prepared from the reaction of (Me3CCH2)2Zn and potassium and sodium, respectively. Also, the structures of these compounds were crystallographically determined and are closely related to the structures of the (trimethylsilyl)methyl zincates described above . 

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