Straight-chain Molecules Research Articles

ChemInform Abstract: Identification of the Sex Pheromone of Scrobipalpula absoluta; Determination of Double Bond Positions in Triple Unsaturated Straight Chain Molecules by Means of Dimethyl Disulfide Derivatization.

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Identification of the sex pheromone of Scrobipalpula absoluta; determination of double bond positions in triple unsaturated straight chain molecules by means of dimethyl disulphide derivatization

The sex pheromone of Scrobipalpula absoluta (Meyrick) (Lepidoptera: Gelechiidae) was identified as a 92:8 mixture of (3 E,8 Z,11 Z)-3,8,11-tetradecatrienyl acetate ( 1) and (3 E,8 Z)-3,8-tetradecadienyl acetate ( 2) through mass spectrometric investigation of the dimethyl disulphide derivatives of excised sex pheromone glands. It is the first time that this method was used for triple unsaturated straight chain molecules. Compound ( 2) was identified as a new pheromone component. A synthetic mixture of the two identified compounds proved to be attractive in wind tunnel experiments.

Nonnatural amino acid yields improved drugs

Chemists from Texas A&M University, College Station, have used a severely constrained analog of an amino acid to make a peptide that has higher biological activity and resistance to degradation than the natural peptide. This substitution of nonnatural for natural amino acids is one approach that medicinal chemists are using to invent peptide drugs of superior efficacy and bioavailability. Texas A&M organic chemistry professor Kevin Burgess told the Division of Organic Chemistry at the ACS national meeting in San Diego that his work with graduate students Kwok-Kan Ho, Chun-Yen Ke, and Dong Yeol Lim uses methionine (Met) that has an extra methylene group, -CH 2 -, between the α- and β-carbon atoms. The extra methylene group ties the normal straight-chain molecule back into a cyclopropane. The researchers nickname the resulting 1-amino-2-methylthiomethylcyclopropanecarboxylic acid E-cyclo-Met, because the amino and methylthiomethyl groups are trans to one another. They also use the name (2S,3S)-cyclo-Met, re...

Laboratory studies of the influence of thin organic films on the neutralization reaction of H 2SO 4 aerosol with ammonia

The neutralization reaction of micro-encapsulated sulfuric acid aerosol with gaseous ammonia has been investigated. Experimental parameters were: influence of different coating substances, coating thickness, relative humidity and reaction time. The reaction of H 2SO 4 aerosol with NH 3 was measured as a function of time by chemical characterization of the particulate and gaseous phase before and after mixing of the reactants in a flow reactor. A remarkable decrease in the reaction rate was observed, depending on molecular structure of the organic coating substance and the thickness of coating. Straight chain molecules like n-hexadecane and n-hexadecanol strongly retard the reaction. Branched chain molecules as coating showed no significant effect, probably because of their inability to form tight films. Naturally occurring organic coating substances affect the neutralization, too. The mass transport resistance of the films investigated are interpreted in terms of the accommodation and reaction coefficient.

A suggested unit cell for it-poly(methyl methacrylate)

A new proposal for the crystal structure of it-PMMA is presented in which the unit cell consists of five straight-chain molecules, each with four polymer units in two combinations of cis-trans methacrylate groups, ctct... and cttt... sequences, in an end-centered monoclinic or an orthorhombic init cell.

Study of microporous carbons by gas chromatographic determination of heats of physisorption

Gas chromatography has been used to measure low-coverage isosteric heats of adsorption ( q st) of n-alkanes (C 1 to C 9), n-alkenes (C 2 to C 4),isopentane, cyclohexane, benzene, 2-methylpentane and 2,2-dimethylbutane on different microporous carbons. The similar q st values between n-alkanes and n-alkenes, cyclohexane and benzene show the non-polar or slight polar surfaces of these adsorbents. The q st values of the molecules with branch chains or bulky shapes are smaller than those of corresponding straight-chain molecules, which may indicate the molecular sieving properties of these slit-shaped microporous carbons. It is also shown that there may be an enhancement of adsorption energy for adsorption of some molecules in wider micropores.

Pancreastatin inhibits insulin secretion as induced by glucagon, vasoactive intestinal peptide, gastric inhibitory peptide, and 8-cholecystokinin in the perfused rat pancreas

Pancreastatin is a 49-amino acid straight chain molecule isolated from porcine pancreatic extracts. In the perfused rat pancreas, this peptide has been shown to inhibit unstimulated insulin release and the insulin responses to glucose, arginine, and tolbutamide. To further explore the influence of pancreastatin on islet cell secretion, the effect of synthetic porcine pancreastatin (a 2-μg priming dose, followed by constant infusion at a concentration of 15.7 nmol/L) was studied on the insulin, glucagon, and somatostatin responses to 1 nmol/L vasoactive intestinal peptide (VIP), 1 nmol/L gastric inhibitory peptide (GIP), and 1 nmol/L 26 to 33 octapeptide form of cholecystokinin (8-CCK). The effect of pancreastatin on the insulin and somatostatin secretion elicited by glucagon (20 nmol/L) was also examined. Pancreastatin infusion consistently reduced the insulin responses to VIP, GIP, and 8-CCK without modifying glucagon or somatostatin release. It also inhibited the insulin release but not the somatostatin output induced by glucagon. These observations broaden the spectrum of pancreastatin as an inhibitor of insulin release. The finding that pancreastatin does not alter glucagon or somatostatin secretion supports the concept that it influences the B cell directly, and not through an A cell or D cell paracrine effect.

ChemInform Abstract: Industrial Application of Shape‐Selective Catalysis

Abstract In the 26 years since the term “shape-selective catalysis” was coined by P. B. Weisz and V. J. Frilette [1] to describe the unique catalytic properties of small pore molecular sieve zeolites, great strides in the use of shape-selective zeolites have been made, both scientifically and technologically. Since then, in addition to small pore zeolites, synthetic medium pore zeolites, such as ZSM-5 [2], ZSM-11 [3], ZSM-22 [4], ZSM-23 [5], ZSM-35 [6], ZSM-38 [7], ZSM-48 [8], etc., have been discovered. The availability of these synthetic medium pore zeolites has expanded the realm of “shape selectivity” beyond the original discovery of selective conversion of straight chain molecules to include certain branched molecules, single-ring aromatics, naphthenes, and nonhydrocarbons with a critical molecular dimension smaller than about 6 A.

Industrial Application of Shape-Selective Catalysis

Abstract In the 26 years since the term “shape-selective catalysis” was coined by P. B. Weisz and V. J. Frilette [1] to describe the unique catalytic properties of small pore molecular sieve zeolites, great strides in the use of shape-selective zeolites have been made, both scientifically and technologically. Since then, in addition to small pore zeolites, synthetic medium pore zeolites, such as ZSM-5 [2], ZSM-11 [3], ZSM-22 [4], ZSM-23 [5], ZSM-35 [6], ZSM-38 [7], ZSM-48 [8], etc., have been discovered. The availability of these synthetic medium pore zeolites has expanded the realm of “shape selectivity” beyond the original discovery of selective conversion of straight chain molecules to include certain branched molecules, single-ring aromatics, naphthenes, and nonhydrocarbons with a critical molecular dimension smaller than about 6 A.

The structure of bone apatite surfaces.

This is a review of the surface chemistry of bone mineral and its synthetic counterpart hydroxyapatite. Small-angle x-ray scattering and low-temperature nitrogen adsorption measurements show bone mineral surfaces range from 100 to 200 m2/g. The heats of adsorption of small molecules on bone and apatite surfaces show that these materials have polarizing surfaces which form strong bonds with polar and polarizable molecules. Water is hydrogen bonded to these surfaces with energies ranging from 23 Kcal/mol, for low coverage, to 11 Kcal/mol after two full layers; the latter value shows that after two monolayers the water is bonded as strongly to the solution as it is to the apatite surface. Stearic acid in cyclohexane adsorbs on bone and apatite surfaces in a closed-packed manner with the straight-chain molecules in parallel array with the end carboxyl groups hydrogen bonded to surface electronegative ions. Synthetic hydroxyapatite has long been used in chromatography because of the bonding capacity apatite surface has for certain proteins and polynucleotides. The metabolic interplay between bone mineral and the body results from the high magnitude and high reactivity of the mineral surface.

Liquid Transportation Fuels From Nova Scotia Coals

Abstract This paper provides an introduction to the various processes for the liquefaction of coal, including pyrolysis, solvent extraction catalytic hydrogenation and indirect conversion. It then goes on to describe the Scotia Coal Synfuels Project, the Initial phases of which are currently underway. Introduction The utilization of coal in Canada and the United States will increase significantly over the next several decades in an effort to reduce our dependence on foreign oil sources. This strategy combined with a delicate supply/demand balance for petroleum products has prompted considerable interest in the production of liquid fuels from coal. During the past fifty years, technological advances in coal conversion have been made in several countries around the world. The objective of this paper is to discuss briefly the methods of converting coal into liquid fuels and outline the activities of the Scotia Coal Synfuels Project, a consortium of five major Canadian companies formed to determine the feasibility of producing liquid transportation fuels from the indigenous coal resources of Cape Breton. Coal has a much lower atomic ratio of hydrogen to carbon than natural petroleum. Therefore, in order to liquefy coal it is essential to increase the hydrogen-to-carbon ratio to higher levels typical of liquid fuels. However, increasing the hydrogen content of coal to + 10% does not mean that the liquids that are produced will be similar or have the same uses as petroleum-derived liquids of the same hydrogen content. The basic reason for this is that petroleum-derived liquids are mostly straight-chain molecules which are termed aliphatic, whereas those derived from coal are mostly ring-type molecules which are called aromatic. The ring-type structure of coal liquids is directly related to the fundamental structure of coal itself. Although the structure of coal is complex, there is a rather general agreement that the skeletal structure of bituminous coal is mostly aromatic. Recent work indicates that ring clusters range from one to perhaps seven rings, the average cluster being comprised of about three rings(l). It is known that about 70% of all carbon atoms are in aromatic rings, but only about 23% of the hydrogen atoms are bound to aromatic carbon atoms(2). The aromatic and hydroaromatic carbons form the skeletal structures aliphatic carbon is found in side-chains and bridges connecting the clusters. Process Schemes to Produce Coal Liquids Known processes for converting coal into liquid fuels can be classified into four broad categories: pyrolysis, solvent extraction, catalytic hydrogenation and indirect liquefaction. These approaches to liquefaction differ primarily in the degree of processing severity. Pyrolysis Pyrolysis, also known as destructive distillation or carbonization, is the least severe approach. (Figure in full paper) general process scheme. Pyrolysis involves the heating of coal in the absence of air or oxygen to yield liquids, gases and char. In this method, the hydrogen-to-carbon ratio is increased because carbon is removed from the system as a solid residue.

Identification of the cuticular hydrocarbons of the horn fly and assays for attraction

Horn fly cuticular paraffin and monoolefin hydrocarbons were chemically identified and assayed for biological activity as attractants. The majority of the paraffins were odd-numbered, straight-chain molecules 21-29 carbons in length; much smaller amounts of even-numbered, straightchain molecules 22-28 carbons in length and methyl-branched compounds were also present. At least 80% of the monoolefin consisted of straight-chain molecules 23, 25, and 27 carbons in length, two of which have been identified as sex pheromones in other muscoid species. The hydrocarbon profiles among sexes and strains (laboratory and wild) were very similar except for wild females, which showed quantitative differences from the other sources. However, only females showed significant (albeit low) responses to some test materials, both synthetic and natural, and activity appeared to be centered in the monoolefins.

Glutamate synthase (NADH) from lupin nodules. Specificity of the 2-oxoglutarate site

The binding of substrate analogues including potential alternative substrates, to glutamate synthase (NADH) ( l-glutamate: NAD + oxidoreductase (transaminating) E.C. 1.4.1.14) has been investigated by studying competitive inhibition with respect to 2-oxoglutarate. Binding requires two terminal carboxyl groups on a C 5 straight chain molecule although some C 4 molecules bind weakly. Bulky substituents at C 2 decrease or prevent binding. Glutarate, the most potent inhibitor, binds much less tightly than the substrate. A 2-oxo group in a molecule other than the substrate does not appear to contribute significantly to binding. None of the analogues was able to act as an alternative substrate.

ChemInform Abstract: VIBRATIONAL SPECTRA AND CARBON‐HYDROGEN STRETCHING MODE ASSIGNMENTS FOR A SERIES OF N‐ALKYL CARBOXYLIC ACIDS

The Raman and infrared spectra for the C4, C8, C12, and C16 carboxylic acid series were obtained at liquid nitrogen temperatures, in the 2900 cm−1 spectral region and were compared to spectra for selected branched and straight chain alkane systems. For hexadecanoic acid‐d3 the Fermi resonance interaction between the CD3 symmetric stretching mode and the overtone level of the CD3 asymmetric deformation vibration was examined as a function of physical state. In this example of a negative Fermi resonance perturbation, in which the lower frequency overtone component is more intense than the higher frequency fundamental, the coupling increases as the system passes from either the matrix isolated species or solution phase to the polycrystalline state. The spectra of the carboxylic acid series, as well as the spectra of 2,2,4‐trimethyl pentane and n‐octane, suggest that in the 2900 cm−1 region an analogous Fermi resonance coupling exists between the CH3 symmetric stretching vibration at ∼2938 cm−1 and the 2871 cm−1 overtone transition of the CH3 asymmetric deformation. Unfortunately, the 2930–2940 cm−1 region for the solid systems is further complicated by transitions attributed to crystal interactions. Although the Fermi interaction for the methyl group has been recognized in the simpler halomethane system, for example, it has not been previously discussed in the more general context of significantly larger branched and straight chain molecules. Comparisons of the carboxylic acid spectra in the 2900 cm−1 region have also led to assignments for the α‐CH2 (adjacent to the carbonyl group) and the ω‐CH2 (adjacent to the methyl group) C–H stretching modes.

Vibrational spectra and carbon–hydrogen stretching mode assignments for a series of n-alkyl carboxylic acids

The Raman and infrared spectra for the C4, C8, C12, and C16 carboxylic acid series were obtained at liquid nitrogen temperatures, in the 2900 cm−1 spectral region and were compared to spectra for selected branched and straight chain alkane systems. For hexadecanoic acid-d3 the Fermi resonance interaction between the CD3 symmetric stretching mode and the overtone level of the CD3 asymmetric deformation vibration was examined as a function of physical state. In this example of a negative Fermi resonance perturbation, in which the lower frequency overtone component is more intense than the higher frequency fundamental, the coupling increases as the system passes from either the matrix isolated species or solution phase to the polycrystalline state. The spectra of the carboxylic acid series, as well as the spectra of 2,2,4-trimethyl pentane and n-octane, suggest that in the 2900 cm−1 region an analogous Fermi resonance coupling exists between the CH3 symmetric stretching vibration at ∼2938 cm−1 and the 2871 cm−1 overtone transition of the CH3 asymmetric deformation. Unfortunately, the 2930–2940 cm−1 region for the solid systems is further complicated by transitions attributed to crystal interactions. Although the Fermi interaction for the methyl group has been recognized in the simpler halomethane system, for example, it has not been previously discussed in the more general context of significantly larger branched and straight chain molecules. Comparisons of the carboxylic acid spectra in the 2900 cm−1 region have also led to assignments for the α-CH2 (adjacent to the carbonyl group) and the ω-CH2 (adjacent to the methyl group) C–H stretching modes.

Monolayer Studies of Chiral and Racemic 12-Hydroxyoctadecanoic Acids

Abstract The monolayer properties of chiral and racemic 12-hydroxyoctadecanoic acids (12HOA) have been studied. Both acids showed, in each pressure-area isotherm, a pressure plateau. This was interpreted as a two-dimensional phase transition region: from the expanded monolayer composed of bent chain molecules with both the hydroxyl and carboxyl groups attached to the water surface, to the condensed monolayer composed of straight chain molecules oriented steeply to the water surface. It was suggested by measuring infrared spectra of the collapsed films and the built-up films that the condensed monolayer involves intermolecular hydrogen bonds. Differences between (R)- and dl-12HOA were found in the plateau pressure and its temperature dependence leading to the transition energy. These results were attributed to the formation of a recemic molecular compound during condensation of monolayers of dl-12HOA, prior to collapse, followed by a different manner of hydrogen bonding. Electron microscope observation gave strong evidence for the two-dimensional racemic compound formation. On the basis of these results and the X-ray diffraction data, molecular packing models in the condensed monolayers were proposed.

NEW METABOLIC PRODUCTS OF L-CITRULLINE AND L-HOMOARGININE

Several clinical conditions associated with hyperammonemia are also characterized, in part, by elevated serum and urine levels of citrulline (C), homocitrulline (HC), and homoarginine (HA). Our previous studies on 14C-ureido-HC revealed that HC was converted by rats and mice, and, in vitro, by L-amino acid oxidase to a cyclic derivative (Fed. Proc. 35:1478, 1976). We now report mass spectrometric data which indicate that an L-amino acid oxidase product of (C) is also cyclic.L-HA is also converted by rats and mice, and in vitro, by amino-acid oxidase to yet another unreported compound. The HA metabolite does not react with ninhydrin but does form a hydrazone with dinitrophenylhydrazine, and thus, may be a straight chain molecule. Enzymatic studies suggest that these α-keto derivatives are formed, in vivo, by transamination reactions.These newly discovered metabolites may represent significant pathways for the disposal of HC, C, and HA in clinical situations where they accumulate.

Water and nonelectrolyte permeability of lipid bilayer membranes.

Both the permeability coefficients (Pd's) through lipid bilayer membranes of varying composition (lecithin [L], lecithin:cholesterol [LC], and spingomyelin:cholesterol [SC]) and the n-hexadecane:water partition coefficients (Knc's) of H2O and seven nonelectrolytes (1,6 hexanediol, 1,4 butanediol, n-butyramide, isobutyramide, acetamide, formamide, and urea) were measured. For a given membrane compositiin, Pd/DKnc (where D is the diffusion constant in water) is the same for most of the molecules tested. There is no extraordinary dependence of Pd on molecular weight; thus, given Pd(acetamide), Pd(1,6 hexanediol) is correctly predicted from the Knc and D values for the two molecules. The major exceptions are H2O, whose value of Pd/DKnc is about 10-fold larger, and urea, whose value is about 5-fold smaller than the general average. In a "tight" membrane such as SC, Pd(n-butyramide)/Pd(isobutyramide)=2.5; thus this bilayer manifests the same sort of discrimination between branched and straight chain molecules as occurs in many plasma membranes. Although the absolute values of the Pd's change by more than a factor of 100 in going from the tightest membrane (SC) to the loosest (L), the relative values remain approximately constant. The general conclusion of this study is that H2O and nonelectrolytes cross lipid bilayer membranes by a solubility-diffusion mechanism, and that the bilayer interior is much more like an oil (a la Overton) than a rubber-like polymer (a la Lieb and Stein).

The surface chemistry of bone mineral and related calcium phosphates

A review of the surface chemistry of bone mineral, hydroxyapatite and amorphous calcium phosphate is presented. Small-angle x-ray scattering and low-temperature nitrogen adsorption measurements show the magnitude of bone mineral surface to range from 100–200 m 2/g; the synthetic hydroxyapatite surface can vary from 25–200 m 2/g, while synthetic amorphous calcium phosphate ranges in surface from 20–60 m 2/g, according to the respective preparation conditions. The magnitude of heats of adsorption of certain small molecules (CO, Ar, N 2, H 2O, CH 3OH) on bone mineral and hydroxyapatite show that these are polarizing surfaces that form strong bonds with polar or polarizable molecules; water is hydrogen-bonded to these surfaces with energies ranging from 23 kcal/ mole for low coverage to 11 kcal/mole after two full monolayers; concomitantly, methanol ranges from 24 kcal/mole to 9 kcal/mole after the adsorption of one and a half monolayers. Stearic acid will close-pack perpendicularly on bone apatite surfaces when adsorbed from cyclohexane solution in a way reminiscent of the adsorption of this long, straight-chain molecule on water surface. It is believed that these molecules are hydrogen-bonded to electronegative ions on the apatite surface. Synthetic hydroxyapatite has long been used in chromatographic adsorption columns because of the specific bonding capacity the surfaces have for certain proteins and polynucleotides. The metabolic interrelationship of bone mineral and the body fluids is in great part dependent upon the nature and magnitude of mineral surface. From the surface studies described herein it was suggested that a chemical linkage could exist in bone between the mineral surface and certain free polar groups of collagen.

Occurrence of Insoluble Starch Particles in Enzymatically Saccharified Starch Solution

In enzymatically liquefied and subsequently saccharified starch solution, some materials often remained insoluble. They contain starch particles which are extremely hard to be solubilized. When their content is high, the resulting saccharified liquid is difficult to be filtered and further purified. This difficulty is a serious concern in commercial production of dextrose. A part of the insoluble starch particles is formed during the liquefaction of starch. Lower temperature than 85°C in liquefaction favors formation of the insoluble starch particles. The other part of the insoluble starch particles comes from the original raw materials. Their contents differ from species to species; the lowest in potato starch and the highest in corn starch. It is also observed that the insoluble starch particles are formed upon heatmoisture treatment of starch. These insoluble starch particles are presumably composed of straight chain molecules of starch.