Alkyl chain structure

So in summary, the presence of a chiral centre in a molecule can render nearby geminal pairs of protons non-equivalent. Nearby is not an exact term and varies according to circumstance. Let s consider our molecule again, but this time, replace the -CH2- with an alkyl chain (Structure 6.2). 

The TMS plasma polymer deposited on the oxygen-pretreated steel surface has Si-O-Si or Si-O-alkyl chain structure, which is similar to the film deposited from a mixture of TMS and O2. Oxygen was always found in the plasma film when the steel surface was pretreated with oxygen plasma. The source of oxygen is very likely from the oxide layer. During TMS plasma deposition, oxygen redeposited with the TMS to form the final film. These results were obtained during an in situ experiment, and the treated surface was not exposed to ambient environment before the deposition of plasma polymer of TMS. Therefore, the influence of oxides on the chemical structure of plasma polymer of TMS is quite evident. 

Lin JL, Teplyakov AV, Bent BE (1996) Effects of alkyl chain structure on carbon-halogen bond dissociation and 3-hydride eUmination by alkyl halides on a Cu(lOO) surface. J Phys Chem 100 10721... 

An important constituent of all fatty acids and their derivatives is the alkyl chain. These chains vary in length (number of carbons) and in the extent of branching and polar group substitution. Chains also vary in the type, number, position, and geometric configuration of unsaturated carbon-carbon bonds. Such differences in alkyl chain structure are largely responsible for the broad variation in the biological properties of... 

Recent syntheses of unsaturated fatty acids that differ systematically in alkyl chain structure (9, 10) make it possible to study the influence of unsaturation on a number of chemical and biochemical processes (11). It seemed to us that many questions concerning the influence of alkyl chain structure on fatty acid interfacial properties could be answered better by studying the monomolecular film properties of these compounds. This paper examines the general surface film properties of some cis and trans ethylenic and acetylenic 18-carbon acids. 

Whilst the early reports of intermediate phases concerned systems with reversed curvature [73-76] these were for surfactants where some residual short range order in the polar groups was probably present. There are few definitive reports of fully molten intermediate phases with reversed curvatures. In fact the pattern of how intermediate phases replace the normal bicontinuous cubic phase as alkyl chain size increase only became recognized as systematic studies on homologous series were carried out [37, 66], Here it has required a combination of microscopy, multinuclear NMR and X-ray diffraction to elucidate the structures. Such studies on reversed phases have yet to be carried out, particularly where small variations in alkyl chain structure are made. 

Interfacial pressure measurements in conjunction with vibrational SF spectra of phosphocholines adsorbed to the water/CCU interface provide a clear picture of how alkyl chain structure depends upon interfacial concentration. Namely, as interfadal concentration increases, alkyl chains adopt more of an all trans conformation as reflected... 

Vibrational sum frequency spectroscopy in conjunction with interfacial pressure measurements provide the first direct information about the structure of phospholipid monolayers composed of DLPC, DMPC, DPPC, and DSPC, adsorbed to the interface between two immiscible liquids. Temperature controlled experiments carried out with aqueous solutions of DSPC show the lipid bilayer gel to liquid crystalline phase transition temperature to play a pivotal role in determining interfacial monolayer concentration and alkyl chain structure. Even at equivalent interfacial concentrations longer chain phosphocho-line species form more disordered monolayers with a greater number of gauche defects than shorter chain phosphocholine species, as determined from relative intensities of vibrational bands in the CH stretching region. 

It is well known that for liquid crystalline molecules like the cyanobiphenyl compounds, physical properties such as the clearing points change regularly depending on whether the number of carbon atoms of the alkyl chain is odd or even. This phenomenon has been explained by the molecular linearity for odd or even carbon numbers of the alkyl chains. A similar phenomenon is observed in the case of polyimide (1) with the alkyl chain structures shown in Fig. 5.2.3 [16,17]. 

The nonpolar amino acids (Figure 4.3a) include all those with alkyl chain R groups (alanine, valine, leucine, and isoleucine), as well as proline (with its unusual cyclic structure), methionine (one of the two sulfur-containing amino acids), and two aromatic amino acids, phenylalanine and tryptophan. Tryptophan is sometimes considered a borderline member of this group because it can interact favorably with water via the N-H moiety of the indole ring. Proline, strictly speaking, is not an amino acid but rather an a-imino acid. 

In an elegant series of reactions, it has been demonstrated that 1//-azepines can be forced into adopting the benzene imine structure 8 by bridging the 2- and 7-positions with a trimethyl-ene chain.61 The length of the alkyl chain, however, is critical and the tetramethylene derivative exists solely as the 2,7-bridged l//-azepine (see Section 3.1.1.4.1.3.). 

Examinations of the connection between the chemical structure of alkylaryl sulfates and their physical-chemical properties show that solubility, aggregations and adsorption behavior, foam behavior and consistency are determined by the following structural elements the length of the alkyl chain, the position at which the benzene ring is connected to the alkyl chain, and the substitution pattern of the benzene ring [187,188]. 

It is difficult to find an industrial sector that does not use alcohol sulfates or alcohol ether sulfates. These surfactants are rendered so versatile in their chemical structure through varying their alkyl chain distribution, the number of moles of ethylene oxide, or the cation that it is possible to find the adequate sulfate achieving the highest mark in nearly every surfactant property. This and the relative low cost are the two main reasons for their vast industrial use. 

Generally ether carboxylates are not suitable for a syndet soap because they are waxy due to the ethylene oxide distribution. The solid ether carboxylates with a long alkyl chain and a low degree of ethoxylation have a bad foam. By use of nonethoxylated ether carboxylates, e.g., a carboxymethylated fatty acid monoethanolamide with the structure... 

Sodium a-sulfonated fatty acid esters of long-chain alcohols have a structural effect on the Krafft point different from that of amphiphiles with short alkyl chains [60]. In a series of homologs with the same total carbon number the Krafft points are highest when the hydrophilic alkyl chain lengths in the a-sulfonated fatty acid and the alcohol are fairly long and equal. In this case the packing of the molecules becomes close and tight. 

---