Claude H. Yoder

The structures of some amides obtained from chloromethyldimethylchlorosilane

Abstract A series of amides of the type RCONR′[CH 2 Si(CH 3 ) 2 Cl] were prepared by the reaction of chloromethyldimethylchlorosilane with a series of N-alkyl, N-aryl, and trimethylsilyl amides. The structure of the compound obtained from reaction with bis(trimethylsilyl)acetamide was previously determined by x-ray analysis and is used to rationalize the NMR and IR spectra of its 14 N and 15 SN isotopomers. The spectroscopic features of the N-alkyl and N-aryl derivatives are discussed; the derivatives with RCH 3 appear to have the oxygen strongly coordinated to silicon within a 5-membered ring.

Carbon-13 chemical shifts of substituted t-butylbenzenes, phenyltrimethylsilanes and phenyltrimethylgermanes

Abstract Carbon-13 NMR chemical shifts are reported for three series of Group IV aromatics p -XC 6 H 4 Y(CH 3 ) 3 where Y = C, Si and Ge. The shifts for the C(1), C(2), CH 3 and C(α) carbons correlate with the substituent parameters σ, and σ o R , and the slopes of the CH 3 correlations suggest roughly equal transmitting abilities for carbon and silicon. For a given substituent X, the shift of the C(1) carbon varies in the order C>Ge>Si expected from electronegativity considerations. The other ring carbon atoms experience smaller changes corresponding to their respective positions ortho , para , and meta to Y. The shifts of the C(4) and C(2, 6) carbons vary Si>Ge>C, in agreement (for X = N(CH 3 ) 2 with atomic charge values from published CNDO/2 calculations for carbon and silicon which indicate that while silicon exerts an electron-releasing effect through the σ-framework, there is a net π-withdrawal registered at the C(4) and C(2, 6) carbon atoms relative to Y = C.

Reactions of the ambidentate substrate chloromethyldimethylchlorosilane with amines and amides

Abstract Chloromethyldimethylchlorosilane (CMDS) reacts with diethylamine and aniline at the SiCl group to form the corresponding chloromethyldimethylsilylamines. With amides, however, substitution on CMDS occurs at the CCl bond to form compounds with a 5-membered ring containing a 5-coordinate silicon. Reaction of trimethylsilyl amides with CMDS provides the most convenient route to this ring system but with bis(trimethylsilyl) amides, RCON[Si(CH 3 ) 3 ] 2 , it proceeds only when R is small. Reaction of bis(trimethylsilyl)acetamide and N -methyltrimethylsilylacetamide with a variety of substrates of the type X(CH 2 ) n Si(CH 3 ) 2 Y occurs when X = Cl or Br and Y = Cl, Br or N(C 2 H 5 ) 2 and n = 2 but not when n = 3 or Y = OC 2 H 5 , CH 3 , CH = CH 2 , or C 6 H 5 .

Molecular water in nominally unhydrated carbonated hydroxylapatite: The key to a better understanding of bone mineral

Abstract Despite numerous analytical studies, the exact nature of the mineral component of bone is not yet totally defined, even though it is recognized as a type of carbonated hydroxylapatite. The present study addresses the hydration state of bone mineral through Raman spectroscopic and thermogravimetric analysis of 56 samples of carbonated apatite containing from 1 to 17 wt% CO3, synthesized in H2O or D2O. Focus is on the relation between the concentration of molecular water (as distinguished from hydroxyl ions) and the concentration of carbonate in the apatite. Raman spectra confirm the presence of molecular water as part of the crystalline structure in all the aqueously precipitated carbonated apatites. TGA results quantitatively document that, regardless of the concentration of carbonate in the structure, all hydroxylapatites contain ~3 wt% of structurally incorporated water in addition to multiple wt% adsorbed water. We spectroscopically confirmed that natural bone mineral also contains structurally incorporated molecular H2O based on independent analyses of bone by means of spectral stripping (subtracting the spectrum of collagen from that of bone) and chemical stripping (chemically removing the collagen content of bone prior to analysis). Taken together, the above data support a model in which water molecules densely populate the apatite channels regardless of the abundance of hydroxyl vacancies. We hypothesize that water molecules keep the apatite channels stable even when 80% of the hydroxyl sites are vacant (typical in bone), hinder carbonate ions from substituting for hydroxyl ions in the channels, and help regulate chemical access to the channels (e.g., ion exchange, entry of small molecules). Our results show that bone apatite is not a “flawed hydroxylapatite,” but instead a definable mineralogical entity, a combined hydrated-hydroxylated calcium phosphate phase of the form Ca10-x[(PO4)6-x(CO3)x](OH)2-x·nH2O, where n ~ 1.5. Water is therefore not an accidental, but rather an essential, component of bone mineral and other natural and synthetic low-temperature carbonated apatite phases.

A Tin-119 NMR investigation of phosphine and phosphine oxide adducts of organotin chlorides

The stoichiometry and structure of phosphine and phosphine oxide adducts of Ph3SnCl, R2SnCl2 (R=Et, Pr, Bu, t-Bu, and Ph), and RSnCl3 (R=Bu and Ph) were studied with Sn-119 spectroscopy. The shift of the Sn-119 resonance to a lower frequency upon adduct formation, the multiplicity of the resonance, the variation of P-31-Sn-119 coupling with the nature of the substituent, and the change in structure of the peaks with concentration and temperature were all used to determine stoichiometry and structure. The organotin chloride adducts readily exchange with base or with other adducts. The diorganotin dichlorides form only 1:1 adducts with tributylphosphine (TBP), even at high base to acid ratios, but most form 1:2 adducts (as several geometric isomers) with phosphine oxides at mole ratios above 1:1. The lower dialkyltin dichlorides prefer to form 1:1 adducts (at 1:1 mole ratios) with TBP rather than tributylphosphine oxide (TBPO), whereas diphenyltin dichloride and di(t-butyl)tin dichloride prefer TBPO adduct formation. The reactions of the trihalides with TBP and TBPO are complicated by aryl transfer or displacement of chloride by base and consequent ion formation.

Geochemical applications of the simple salt approximation to the lattice energies of complex materials

Abstract The lattice energies for a variety of compounds that can be classified as double salts are calculated by summing the lattice energies of the constituent simple salts. A comparison with the lattice energies obtained from the Born-Haber or other thermodynamic cycles shows that the simple salt approximation reproduces these values generally to within 1.2%, even for compounds that have considerable covalent character. Application of this method to the calculation of the lattice energies of silicates, using the sum of the lattice energies of the constituent oxides are, on average, within 0.2% of the value calculated from the experimental enthalpies of formation. The implications of the simple salt approximation for the thermodynamics of geochemically important processes are discussed.

Nuclear magnetic resonance studies of the bonding in aryltrimethylsilanes and germanes, aryldimethylphosphines and arsines, and arylmethylsulfides

Abstract Methyl chemical shifts and 13 C-H coupling constants were measured for the title compounds. Reasonably good (r>0.9) linear correlations between chemical shifts and Hammett σ-constants were found for all series, and the relative slopes of these lines were interpreted in terms of the mode of transmission of substituent effects to the methyl site. The effects of the Si(CH 3 ) 3 , Ge(CH 3 ) 3 , P(CH 3 ) 2 , As(CH 3 ) 2 , and SCH 3 groups on the methyl chemical shifts and coupling constants of toluenes, anisoles, and dimethylanilines were also determined and related to the electronic nature of these groups.

Inclusion complexes of alcohols with α-cyclodextrin

Calorimetric studies of the inclusion complexes of straight and branched alcohols and of diols with alpha-cyclodextrin (α-CD) have been carried out in water solvent. The data suggest that straight and branched chain alcohols enter the cavity of α-CD alkyl end first. The hydroxyl group hydrogen bonds to the outer oxygen ring of the cyclodextrin. For branched chain alcohols the longer alkyl part of the molecule penetrates the α-CD cavity up to the hydroxyl group. Diols form two hydrogen bonds to the outer oxygen ring of the cyclodextrin with some penetration into its interior.

Effect of carbonate incorporation on the hydroxyl content of hydroxylapatite

Abstract Mechanisms for the incorporation of carbonate into minerals of the apatite group have been explored in both the geological and medical literature. An important problem with respect to biological apatite, which requires further clarification, is the hydroxyl content of the carbonated apatite of bone. Recent studies reveal bone apatite to contain only ~20 mol.% of the hydroxyl content of stoichiometric hydroxylapatite, with negligible chloride or fluoride. We investigated the hypothesis that the development of vacancies in the hydroxyl channel sites is a charge-balancing mechanism for the substitution of carbonate ions into hydroxylapatite. Raman spectroscopic analyses of synthetic carbonated apatites (containing 1 to >15 wt.% carbonate) show that their hydroxyl ion concentration correlates inversely with carbonate concentration. The specific relationship between carbonate and hydroxyl concentration in these samples closely follows the theoretical relationship defined by type-B substitution of carbonate for phosphate in the apatite structure. However, the 6-8 wt.% carbonate concentration in bone apatite falls far short of accounting for all of the hydroxyl depletion that occurs in bone apatite. Some of the additional hydroxyl depletion in bone apatite might result from substitution of Na+ for Ca2+, but further mechanism(s), perhaps (HPO4)2- substitution, must also play a significant role.

Application of the simple salt lattice energy approximation to the solubility of minerals

Abstract The simple salt approximation for the lattice energy of double salts is used to provide an estimate of their molar solubilities. These calculations are compared with solubilities obtained from literature thermodynamic data and are within an order of magnitude for about 75% of the 81 minerals and other double salts examined. The solubilities of about two-thirds of the double salts are similar to the solubilities of the less soluble simple salt .constituents,. and the solubilities of the other one-third lie between the solubilities of the .constituents.. In general, the solubilities of a series of salts with different stoichiometries containing the same ions are dependent on both the stoichiometry of the salt and the proportion of the less soluble constituent. This generalization is rationalized with the simple salt approximation and is used to explain the observed stoichiometries of a variety of minerals.