A major challenge in modern society is the reduction of microplastics created by polymers having stable C–C backbones. The chemistry of radical ring-opening copolymerization of cyclic ketene acetals (CKAs) with vinyl monomers in introducing degradable ester units into the C–C backbone is highly promising. Although the corresponding reaction in an aqueous medium should provide biodegradable primary dispersions, the bottleneck is the hydrolytic instability of CKAs. Therefore, in-depth hydrolysis kinetics of CKA (2-methylene-1,3-dioxepane, MDO) at different pH values and temperatures under homogenous and heterogenous conditions are studied to get a “sweet spot” under which emulsion polymerization of MDO might be possible. Depending on the pH, the hydrolysis of MDO undergoes three different mechanisms with slowed hydrolysis kinetics under alkaline conditions. Besides 4-hydroxy-1-butylacetate (4-HBA), other co-hydrolysis products were detected, leading to the autocatalysis effect. The fast MDO hydrolysis during emulsion copolymerization with vinyl acetate led to the formation of polymers with extremely less incorporation of ring-opened MDO units. Degradation tests of the corresponding emulsion copolymers compared with copolymers prepared in solution confirmed the low incorporation ratio of MDO. The results and discussion presented in this work will be a strong guideline for future emulsion copolymerizations of CKAs.

The title compound was obtained in a four-step synthesis start-central benzene ring intact. LiAIHl reduction of the resulting ing from (4-methoxypheny1)silane. Owing to the presence of hexakis[(trifluoromethylsulfonyloxy)silyl]benzene (5) finally activating p-methoxy groups in the key intermediate hexa-leads to crystalline, sublimable, air-stable C6(SiH3j6 (S), m.p. kis[(4-methoxyphenyl)silyl]benzene (4), the peripheral aryl 165°C. In the crystals (triclinic, space group Pi) the structure groups can be cleaved selectively from the silicon atoms with of the centrosymmetrical molecules approaches very closely trifluoromethanesulfonic acid, leaving the Si -C bonds to the point group D3dr as predicted from theoretical considerations.We report on the synthesis of hexasilylbenzene, C6(SiH3)6 (6). This molecule is of considerable interest regarding its structure and energy characteristics, but also as a precursor for cation and anion radicals, as an electron-rich ligand for organometallic compounds, as a multi-silicon-functional synthon, and as a single-component source of silicon and carbon for the deposition of silicon carbide. The compound is expected to suffer from very little, if any, sterical crowding as compared to the partially or fully methylated homologues Cb(SiMe& and C6(SiMe3)6, which were shown to have extremely puckered benzene ringsL',21. Though not prepared previously, the compound has been included in patents for chemical uapour deposition of surface coatings[31.Recent attempts to synthesize C6(SiH3)6 starting from phenyl-or (4-methylpheny1)silane were unsuccessful, since in the critical step (below) random cleavage by acid occurred with the key intermediates C6(SiH2Ph)6 and C6(SiH2C6H4-4-Me)6[41. Therefore, in a new effort, aryl groups with more strongly activating substitutents were chosen for the protecting aryl groups, which were expected to favour peripheral cleavage over "central" cleavage.Trichloro(4-methoxypheny1)silane (1) is prepared and converted into (4-methoxypheny1)silane (2)

, By varying their stoichiometry these compounds can be used as single source feedstock gases for layers with tailor-made composition. In a new approach to the epitaxial deposition of silicon carbide, halogencontaining feedstock gases are expected to show improved properties owing to a greater reversi bility of the deposition process. W hereas polysilylalkanes halogenated at carbon are well rep resented in the literature [1 0 , 1 1 ], only limited information is available on the corresponding alkenes. The low thermal stability of polysilylated haloalkanes makes these compounds unsuitable for practical processes. The ethene analogues are expected to exhibit greater thermal stability and to be more amenable regarding storage and con * Reprint requests to Prof. Dr. H. Schmidbaur. tinuous handling. Although several sterically crowded polysilyl ethenes have been the subject of investigations of their molecular structure, dy namics and energy characteristics [12][13][14][15][16], the num ber of structurally characterized compounds is still small. Following work on silylalkanes, our more recent studies have therefore focused on silyl olefines. In the course of these investigations we have undertaken the X-ray structure determ i nations of bis(trichlorosilyl)acetylene and of the two most crowded trichlorosilylethenes, tris(trichlorosilyl)ethene and tetrakis(trichlorosilyl)-ethene.

This version is available at https://strathprints.strath.ac.uk/10627/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. The structures of 1,3,5-trisilylbenzene and hexasilylbenzene in the gas phase have been determined by electron diffraction, and that of 1,3,5-trisilylbenzene by X-ray crystallography. The structures of three trisilylbenzene isomers, three tetrasilylbenzenes, pentasilylbenzene and hexasilylbenzene have been computed, ab initio and using Density Functional Theory, at levels up to MP2/6-31G*. The primary effect of silyl substituents is to narrow the ring angle at the substituted carbon atoms. Steric interactions between silyl groups on neighbouring carbon atoms lead first to displacement of these groups away from one another, and then to displacement out of the ring plane, with alternate groups moving to opposite sides of the ring. In the extreme example, hexasilylbenzene, the SiCCSi dihedral angle is 17.8(8)• .

The molecular structures of trans-1,2-dichloro-1,2-disilylethene and 1-bromo-1-silylethene have been determined by gas-phase electron diffraction (GED) and ab initio molecular orbital calculations (MP2/6-311G). Both compounds were found to have highly asymmetric coordination around the carbon atoms with [ab initio (r(e))/GED (r(a))] C=C-Cl [117.0/117.0(2) degrees] and C=C-Si [126.2/128.1(1) degrees] in the C(2)(h) structure of trans-1,2-dichloro-1,2-disilylethene and C=C-Br [119.2/120.7(4) degrees] and C=C-Si [125.0/125.0(4) degrees] in the C(s) structure of 1-bromo-1-silylethene. Other important structural parameters for trans-1,2-dichloro-1,2-disilylethene are C=C [135.2/134.5(3) pm], C-Si [189.4/187.9(2) pm], and C-Cl [175.1/174.9(1) pm], and C=C [134.2/133.4(2) pm], C-Si [187.8/187.2(3) pm], and C-Br [191.3/191.0(3) pm] for 1-bromo-1-silylethene. Further ab initio calculations were carried out on CH(2)CRX and trans-(CRX)(2) (R = SiH(3), CH(3), or H; X = H, F, Cl, or Br) to gauge the effects of electron-withdrawing and electron-donating groups on the structures. They reveal some even more distorted structures. The asymmetric appearance of these molecules can largely be accounted for by valence shell electron pair repulsion theory.