Jimmy Jones

29Si and 13C NMR Studies of organosilicon chemistry. IX. Silatranes

Abstract Silicon-29 and carbon-13 NMR spectra were obtained for four silatranes and for the corresponding triethoxysilanes. The chemical shift data are discussed in terms of the pentacoordination at silicon in the silatranes. The vinyl region 1 H and coupled 13 C spectra of vinylsilatrane and vinyltriethoxysilane were computer-fitted to yield values of chemical shifts and coupling constants. Carbon-13 spin-lattice relaxation times and 13 C-{ 1 H} nuclear Overhauser enhancements are presented for all the compounds studied. Similar information was obtained for 29 Si for the two compounds with direct SiH bonds.

Silicon-29 NMR studies of aqueous silicate solutions part 7: Exchange rates between anions☆

Abstract Silicon-29 NMR evidence is presented regarding the linewidths and the rates of chemical exchange between the smaller silicate anions in alkaline aqueous solutions of sodium and potassium silicates. It is found that the linewidths of different species vary, being relatively large for the dimer under most conditions. Moreover, as well as decreasing with increasing temperature, linewidths also appear to decrease with increasing pH. Some semi-quantitative values for lifetimes in particular solutions under given conditions are presented, but it is emphasized that these are minimum values, since there may be other origins for line-broadening.

Silicon-29 and carbon-13 NMR studies of organosilicon chemistry: X. The structure of Si8O11(OSiMe3)10

Abstract Trimethylsilylation of tetramethylammonium silicate produced a compound of formula C 30 H 90 O 21 Si 18 . NMR studies using the 13 C and 29 Si nuclei have shown that the structure of this compound is related to a double four-membered cage by the replacement of one SiOSi bridge by trimethylsiloxy units.

New apparatus for liquid sampling in electron spectroscopy: He(I) spectra of the vapours and surfaces of methanol, ethanol, 1-heptanol and 1-decanol

Abstract A new apparatus is described for maintaining either a flowing or a stationary liquid surface within an evacuated compartment for the purposes of electron spectroscopy, mass spectroscopy, etc. The liquid is made to flow down a tungsten rod which can be cooled or heated by a saturated slush bath or liquid. The position of the rod is variable so that the liquid surface can be held in the best position and orientation. By varying the rate of flow or by completely stopping the flow of liquid it is possible to examine surfaces at different times after formation and to carry out kinetic studies. The He(I) photoelectron spectra are reported of flowing surfaces of methanol and ethanol at −78°C and also of the vapours above the flow. Spectra of 1-heptanol at 0°C and 1-decanol at 20°C are also given. Contamination of these liquid surfaces with loss of spectral structure occurs in the spectrometer within 30 s to 2 min of formation.

The He(I) photoelectron spectrum of benzyl alcohol-liquid surface and gas phase

Abstract He(I) photoelectron spectra of benzyl alcohol (liquid surface and gas phase) are presented and a simple method is given for the removal of the effects of He(Iβ) impurity. In addition to the general shift to lower ionisation energy usually observed in the spectrum of neutral (uncharged, as opposed to ionic) substances on change of phase from gas to liquid, there are also shifts in the ionisation energies of some bands relative to others: specifically the non-bonding O band shifts on liquefaction by O.5 eV more than the other bands. This relative shift is attributed to hydrogen bonding.

The surface concentrations of binary liquid mixtures measured by UV photoelectron spectroscopy

Abstract By means of He(I) photoelectron spectroscopy the surface concentrations of liquid mixtures of n -decan-1-ol. 1,2-ethanediol, tris(dioxa-3,6-heptyl)amine and hydroxypropionitrile have been determined at ambient temperatures. Measurements of the surface tensions of these mixtures have been made and qualitative agreement is found between the surface compositions and those predicted by the Gibbs adsorption formula.

He(I) photoelectron studies of liquids and gases

Abstract He(I)photoelectron spectra of tetramethyl- p -phenylenediamine, phenol, benzyl alcohol and formamide in gaseous and liquid forms have been measured. The structure underlying these spectra is enhanced by plotting them in the form of their second derivatives. Comparison of the spectra of the gas phase and liquid surface reveals the effects of intermolecular interaction and sometimes enables the determination of the molecular form of the surface layer.

Surface activity of solutes in hydroxypropionitrile studied by He(I) photoelectron spectroscopy - EGG lecithin, sodium oleate, malachite green and tris-(dioxa-3,6-heptyl)amine

Abstract We have used He(I) photoelectron spectroscopy to measure the percent surface coverage for substances dissolved in hydroxypropionitrile, HO(CH 2 ) 2 CN. The concentration at which 100% surface coverage is achieved, C 100 , is an inverse measure of surface activity. Measured values of log 10 ( C 100 ), with C 100 in molarity units, in hydroxypropionitrile at 20°C are (in order of diminishing surface activity): −3.85 (egg lecithin), −2.85 (sodium oleate), −0.64 (malachite green hydroxide), and 0.34 [tris(dioxa-3,6-heptyl)amine].

The He(I) photoelectron spectra of lipid phosphatides

Abstract Complete layers of some lipids are formed spontaneously on the surfaces of solutions of sufficient concentration in certain solvents, e.g. phosphatidylcholine (egg lecithin) and phosphatidylinositol (wheat germ) dissolved in hydroxypropionitrile. The He(I) photoelectron spectra of phosphatides in such layers contain: (1) a broad band, assigned to alkyl groups, with maximum intensity at about 11 eV, (2) another broad band at about 8 eV, assigned to the PO - 4 group with about 1 % of the band area of (1).

Auger and electron energy loss studies on liquid surfaces

Abstract The effects of surfactant layers on the Auger and electron energy loss spectra of liquid formamide and hydroxypropionitrile are reported. The characteristic structure of formamide remains in the loss spectrum even when there is complete surface coverage as verified by the Auger spectra.