Silicon protonic acids

The alkynyl-silicon bond is not cleaved readily by protonic acids, but cleavage can be accomplished by Ag+ under mild conditions . For example, treatment of 237 with aqueous ethanolic silver nitrate followed by liberation of the free alkyne from the silver salt by aqueous KCN gave 238 in 80% yield. 

Divalent silicon species react readily with protonic acids, e.g., MCjSi from (MejSi) photolysis reacts with alcohols and amines ... 

Problems presented by this approach included the presence of impurities contributed by the diene, etc. The approach currently used in our laboratory involves direct GC/flame ionization detector (FID) analysis on medium- or wide-bore cyanopropyl/ phenyl/methyl silicone bonded-phase columns. The key prerequisite is to stabilize the sample against anionic polymerization by prior addition of a low level of an appropriate protonic acid stabilizer. 

When a Br nsted base functions catalytically by sharing an electron pair with a proton, it is acting as a general base catalyst, but when it shares the electron with an atom other than the proton it is (by definition) acting as a nucleophile. This other atom (electrophilic site) is usually carbon, but in organic chemistry it might also be, for example, phosphorus or silicon, whereas in inorganic chemistry it could be the central metal ion in a coordination complex. Here we consider nucleophilic reactions at unsaturated carbon, primarily at carbonyl carbon. Nucleophilic reactions of carboxylic acid derivatives have been well studied. These acyl transfer reactions can be represented by... 

A gas ehromatographic analysis on the produet by the submitter, using an 0.3 x 80 cm. column packed with 10% silicone rubber (SE-30) supported on acid-washed, 60-80 mesh Chromasorb P at 80°, exhibited a single peak. The retention times of di-ter(-butyl malonate, di-fert-butyl diazomalonate, and p-toluenesulfonyl azide were 2, 6, and 9 minutes, respectively. The purity of the product obtained by the checkers was estimated from proton magnetic resonance spectra to be ca. 94%, the remainder being di-tert-butyl malonate. 

A new route to alkyl silicates and organosiloxanes is described. This route has three steps. These are (1) the protonation of a silicate (obtained by collection, mining, or laboratory or commercial synthesis), (2) the esterification of the silicic acid formed by the protonation, and (3) the organodealkoxylation of the alkyl silicate resulting from the esterification. An important feature of this route is that it does not depend on elemental silicon. The route is illustrated with the synthesis of (EtO)4Si from 7-Ca2SiC>4,... 

Compounds 9-16 were found to undergo an acidic reaction in aqueous solution.21 Possibly, these zwitterionic A5S/-silicates behave as Lewis acids reacting with the Lewis base OH- to generate protons (2 H20 OH- + H30+). This interpretation is supported by the observation that the related compounds 6 and 7 react with [HNMe3]F in aqueous solution to yield the ionic A6S/-silicates 25 and 26, respectively (Scheme 4 the Lewis bases F-and OH- are isoelectronic).24 The identity of these hexacoordinated silicon... 

Silicoaluminophosphates (SAPOs), along with their crystalline aluminum phosphate counterparts (ALPOs), first discovered by Union Carbide workers in the early 1970s [41, 42], derive their acidity through the substitution of framework phosphorous by silicon thereby creating the charge imbalance which, when compensated for by protons, creates acidic centers. SAPOs in general have seen limited use in bond-breaking applications primarily due to weaker acidity, framework stability, or technoeconomic reasons. Of the rich variety of structures available,... 

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