Functional polymers. XLVII. Synthesis of various derivatives of ω-alkenoates

A number of derivatives of ω-alkenoates were synthesized in preparation for the synthesis of functional polymers based on α-olefins. For the preparation of most of the methyl esters, the regular esterification of ω-alkenoic acids, specifically 10-undecenoic acid with methanol and sulfuric acid as the catalyst, was most effective. For the preparation of the tert-butyl- and 2-ethylhexyl esters of 10-undecenoic acid, the acid chloride route was found to be most convenient, whereas for the preparation of the corresponding esters of 5-hexenoic acid, our method of choice was the synthesis via the imidazolyl derivative of the acid. 2,2,2-Trifluoroethyl 10-undecenoate and the 2,2-dimethyloxazolidine derivative of 10-undecenoic acid were prepared from the acid and 2,2,2-trifluoroethanol or 2-amino-2-methyl-propanol with p-toluene sulfonic acid as the catalyst. Esters of phenol, 2,6-dimethylphenol, and 2,6-diphenylphenol were synthesized from 3-butenoic and 10-undecenoic acid with trifluoroacetic anhydride.     

Functional polymers LII Synthesis and polycondensation of 2(2,4-Dihydroxyphenyl)2H-1,3-bis[4-carboxy (or 4-carbomethoxy)2H-benzotriazole]

Carboxy- and carbomethoxy derivatives of resorcinols with two benzotriazole substituents have been synthesized. 2(2,4-Dihydroxyphenyl)2H-1,3-bis-(4-carboxybenzotriazole) [2,4-bis(2H-4-carboxybenzotriazole-2-yl)-1,3-dihydroxybenzene] (DCBDH) was prepared by azo coupling of 4-carboxy-2-nitrobenzene diazonium chloride with resorcinol followed by reductive cyclization. 2(2,4-Dihydroxyphenyl)2H-1,3-bis(4-carbomethoxy-benzotriazole) [2,4-bis-(2H-4-carbomethoxy-benzotriazole-2-yl)-1,3-dihydroxybenzene] (DCMBDH) was obtained by esterification of the free dicarboxylic acid with methanol. The compounds were characterized by their elemental analyses and melting points, and by their IR, UV,¹H NMR, and¹³C NMR spectra.Copolycondensations were carried out to incorporateDCBDH orDCMBDH into polyamides or polyesters. The condensation copolymers were briefly characterized.Functional Polymers LI:M. D. Purgett,W. J. MacKnight, andO. Vogl, Polym. Eng. and Sci.27(19), 1461 (1987)     

New monodentate chiral phosphite ligands for asymmetric hydrogenation

We report the synthesis of new chiral monodentate phosphite ligands with a biphenyl backbone, the axial chirality of which is introduced early in the synthesis and locked by a chiral alkylenedioxy bridge. We also describe results obtained with these ligands in rhodium-catalysed asymmetric hydrogenation of various substrates.     

Head-to-head polymers. XV. A facile synthesis of 2,3-disubstituted succinates and butanediols-1,4

A synthetic approach that makes symmetrically 2,3-dialkyl-substituted succinates and compounds prepared from 2,3-dialkyl-substituted succinates easily available has been developed. Coupling of α-bromoalkanoic esters with a zinc/copper couple produced in about 40% yield 2,3-disubstituted succinates which were reduced with LiAlH₄ to 2,3-disubstituted butanediols-1,4 in nearly quantitative yields. Some 2,3-disubstituted butanediols-1,4 were cyclodehydrated under reduced pressure with KHSO₄ to 3,4-disubstituted tetrahydrofurans or acetylated and the diacetyl compounds pyrolyzed at 525°C to 2,3 disubstituted butadienes-1,3. The length of the alkyl chains of the 2,3-dialkylsuccinates and consequently the 2,3-dialkylbutanediols-1,4 ranged from C₂ to C₁₆. 2,3-Disubstituted butanediols-1,4, 2,3-disubstituted butadienes-1,3, and 3,4-disubstituted tetrahydrofurans are interesting monomers for polymerization experiments.     

Higher aliphatic polyaldehydes. IV. Transitions in poly(n-valeraldehyde), poly(n-hexaldehyde), poly(n-heptaldehyde), and poly(n-octaldehyde)

Crystalline polymers of n-valeraldehyde, n-hexaldehyde, n-heptaldehyde, and n-octaldehyde were prepared by anionic polymerization with lithium tertiary butoxide as the initiator at low temperatures. The polymers were end-capped with acetic anhydride, and their thermal stability was studied primarily by DTG. It was found that all polymers degrade rapidly above 150°C. All polymers show a dual melting-point behavior. The first melting region, which is associated with the melting of the side chain, is 80–85°C for poly(n-valeraldehyde); 87–90°C for poly(n-hexaldehyde); 78–101°C for poly(n-heptaldehyde); and 41–69°C for poly(n-octaldehyde). Annealing and quenching of the samples showed that this melting-point region consisted of several endotherm peaks whose intensity changed according to the thermal history of the sample. Although the samples are apparently highly crystalline, the side-chain crystallinity is apparently only in the 20% range.     

Helical conformations of isotactic polyacetaldehyde and other isotactic polytrihaloacetaldehydes

Minimum potential energy helical conformations for a family of four isotactic polyacetaldehydes have been determined. Our results indicate that all of the polymers form irrational helices. Comparisons have been made with the reported structures for two of these stereoregular polymers based on earlier X-ray diffraction data. c-Axis values associated with the pitch of the helix for polyacetaldehyde and for polytrichloroacetaldehyde (polychloral) were experimentally measured to be 0.48 and 0.51 nm, respectively. Our calculated conformations afforded values for a helix pitch of 0.47 and 0.52 nm, respectively, which derive from a 3.9/1 helix for polyacetaldehyde and a 3.7/1 helix for polychloral. The structure for polytribromoacetaldehyde (polybromal) was predicted to be similar to that for polychloral. For polytrifluoroacetaldehyde (polyfluoral) and polyacetaldehyde, a number of helical conformations with similar energies were found. All of these conformations could be related to the polychloral helical structure. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1855–1860, 1998     

Stereospecific polymerization and chiral initiation,chiral crystallization and chiral nucleation

Helical macromolecules which are configurationally and conformationally specific can now be synthesized. Monomer structures must be selected that demand spacial restriction for monomer addition. High specificity of monomer addition during polymerization has parallels in crystallization of some inorganic salts from aqueous solution. Initiation of highly specific polymerizations with chiral initiators give helical polymers with substantial one-handedness. Nucleation of certain inorganic salts with chiral nucleating agents, the enantiomers of the salts produce enantiomerically pure chiral salts.     

SI-traceable certification of the amount content of cadmium below the ng g–1 level in blood samples by isotope dilution ICP–MS applied as a primary method of measurement

The development and implementation of a method for the certification of cadmium in blood samples at low ng g^–1 and sub ng g^–1 levels is described. The analytical procedure is based on inductively coupled plasma isotope dilution mass spectrometry (ICP–IDMS) applied as a primary method of measurement. Two different sample digestion methods, an optimized microwave digestion procedure using HNO₃ and H₂O₂ as oxidizing agents and a high-pressure asher digestion procedure, were developed and compared. The very high salt content of the digests and the high molybdenum content, which can cause oxide-based interferences with the Cd isotopes, were reduced by a chromatographic matrix separation step using an anion-exchange resin. All isotope ratio measurements were performed by a quadrupole ICP–MS equipped with an ultrasonic nebulizer with membrane desolvator. This sample introduction set-up was used to increase sensitivity and minimize the formation of oxides (less MoO⁺ interference with the Cd isotopes). Because of the very low Cd concentrations in the samples and the resulting need to minimize the procedural blank as much as possible, all sample-processing steps were performed in a clean room environment. Detection limits of 0.005 ng g^–1 Cd were achieved using sample weights of 2.7 g. The method described was used to re-certify the cadmium content of three different blood reference materials from the Community Bureau of Reference (BCR) of the European Commission (BCR-194, BCR-195, BCR-196). Cadmium concentrations ranged between ～0.2 ng g^–1 and ～12 ng g^–1. For these materials, SI-traceable certified values including total uncertainty budgets according to ISO and Eurachem guidelines were established.     

Addition polymers of aldehydes

The polymerization of aldehydes has played a considerable role in the progress of chain reaction polymerization and has significantly contributed to our knowledge of polymer science. Polyformaldehyde, as homopolymer and copolymer, plays an important role as a significant niche product in engineering plastics use. Higher aldehyde polymerization demonstrates the importance of stereospecificity and the ceiling temperature of polymerization. A discussion of haloacetaldehyde polymers is reserved for an upcoming article. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2293–2299, 2000