A Low-temperature Infrared Study of Self-association in Thiolic Acids

1973 ◽  
Vol 51 (9) ◽  
pp. 1443-1447 ◽  
Author(s):  
R. Bicca de Alencastro ◽  
C. Sandorfy
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Carbonyl Groups ◽  
Infrared Study ◽  
Text Type ◽  
Stretching Vibration ◽  
Self Association ◽  
High Concentrations ◽  
Associated Species ◽  
Anharmonicity Constants

The i.r. spectra of thioloacetic and thiolobenzoic acids were measured in both the fundamental and first overtone regions of the S—H stretching vibration, in a mixture of CCl3F and C2F4Br2, at temperatures ranging from 20 to −190 °C. [Formula: see text] type bonds are formed at low temperatures or at high concentrations of solute. Two different species can be detected. The first is probably an open dimer and the second a cyclic dimer. The S—H anharmonicity constants are of the order of 50–60 cm−1, for both free and associated species, and have about the same value as in aliphatic or aromatic mercaptans. Carbonyl groups have lower anharmonicities. Their value is about 10 cm−1, for both free and associated species.

A Low Temperature Infrared Study of Self-association in Thiols

1972 ◽  
Vol 50 (22) ◽  
pp. 3594-3600 ◽  
Author(s):  
R. Bicca de Alencastro ◽  
C. Sandorfy
Keyword(s):  
Hydrogen Bonding ◽  
Low Temperature ◽  
Infrared Spectra ◽  
Low Temperatures ◽  
Infrared Study ◽  
Text Type ◽  
Stretching Vibration ◽  
Aliphatic Thiols ◽  
Self Association ◽  
Associated Species

The infrared spectra of several aliphatic thiols and of benzenethiol were measured between 2400 and 2700 cm−1, and 4800 and 5300 cm−1 in a 1:1 mixture of CCl3F and C2F4Br2, at temperatures ranging from 20 to −190 °C. Dimerization takes place at low temperatures and more highly associated species also appear. Free S—H groups are present in the solutions as well as in the pure liquids, even at the lowest temperatures. The association is of the [Formula: see text] type in aliphatic thiols; both [Formula: see text] and [Formula: see text] bonds are found in the case of benzenethiol and α-toluenethiol. Hydrogen bonding has little effect on the anharmonicity of the S—H stretching vibration.

A Low Temperature Infrared Study on the Association of Thiols with Pyridine and Triethylamine

1973 ◽  
Vol 51 (7) ◽  
pp. 985-990 ◽  
Author(s):  
R. Bicca De Alencastro ◽  
C. Sandorfy
Keyword(s):  
Low Temperatures ◽  
Bond Formation ◽  
Infrared Study ◽  
Hydrogen Bond Formation ◽  
Text Type ◽  
Predominant Species ◽  
Type Complex ◽  
Proton Donors ◽  
Stretching Vibration ◽  
Associated Species

The infrared spectra of solutions containing propane-1-thiol or benzenethiol as proton donors, and pyridine or triethylamine as proton acceptors were measured down to about −100 °C. The dependence of hydrogen bond formation on concentration and temperature was studied at the fundamental and overtone region of the S—H stretching vibration. The predominant species is found to be a 1:1 [Formula: see text] type complex. In addition, evidence was found for the existence of more highly associated species at low temperatures. Thiol–thiol [Formula: see text] type hydrogen bonds are also present in the case of benzenethiol–pyridine mixtures.

Low Temperature Infrared Study of Hydrogen Bonding in Dissolved Pyrrole and Indole

1973 ◽  
Vol 51 (7) ◽  
pp. 1075-1082 ◽  
Author(s):  
Marie-Claude Bernard-Houplain ◽  
C. Sandorfy
Keyword(s):  
Hydrogen Bonding ◽  
Low Temperature ◽  
Spectroscopic Methods ◽  
Infrared Study ◽  
Stretching Vibration ◽  
Self Association ◽  
Associated Species

Self-association by hydrogen bonding in the case ot pyrrole was studied by i.r. spectroscopic methods. The fundamental first and second overtones of the NH stretching vibration were measured at different concentrations and at temperatures ranging from 22 to −190 °C. The existence of at least two associated species in solution has been ascertained. 2,5-Dimethylpyrrole and indole were also studied and gave similar results.

Electrophysical properties of the (SnSe)1−x–(SmSe)x solid solutions at high and low temperature

2019 ◽  
Vol 34 (01) ◽  
pp. 2050008
Author(s):  
V. A. Abdurahmanova ◽  
N. M. Abdullaev ◽  
Sh. S. Ismayilov
Keyword(s):  
Activation Energy ◽  
Electrical Conductivity ◽  
Low Temperature ◽  
Solid Solutions ◽  
Low Temperatures ◽  
Electrophysical Properties ◽  
Type Specimens ◽  
Text Type ◽  
Donor Type ◽  
Text Density

The temperature range of [Formula: see text] = 77–770 K in the system alloys: Holl coefficient [Formula: see text], thermo-emf [Formula: see text], electric conductivity [Formula: see text], measured [Formula: see text]-density of components and analyzed. It has been established that samarium additive atoms contain donor-type properties and the effectiveness increases with the temperature increase: up to 40% proportional to [Formula: see text] K in [Formula: see text]-type specimens, whereas in [Formula: see text]-type samples this increase is higher and covers the contents of pH varying from [Formula: see text] to [Formula: see text]. An electrical conductivity of compounds increased due to the carrier activation with further increase of temperature. The activation energy of carriers at low temperatures ([Formula: see text] K) is [Formula: see text] eV for [Formula: see text] mol.% and [Formula: see text] mol.% compounds at [Formula: see text] = 77–320 K and for [Formula: see text] mol.% and [Formula: see text] mol.% compounds are [Formula: see text] eV. [Formula: see text] const at [Formula: see text]–400 K for [Formula: see text] mol.% and [Formula: see text] mol.% compounds, and passing with minimum increases at [Formula: see text] = 400–500 K.

Linear oligopeptides. 118. Preferred conformations and modes of self-association of the fluoren-9-ylmethoxycarbonyl amino acid derivatives

1984 ◽  
Vol 62 (12) ◽  
pp. 2661-2666 ◽  
Author(s):  
Giovanni Valle ◽  
Gian Maria Bonora ◽  
Claudio Toniolo
Keyword(s):  
Solid State ◽  
Amide Bond ◽  
Experimental Result ◽  
Carbonyl Groups ◽  
Protecting Group ◽  
X Ray Diffraction ◽  
Aminoisobutyric Acid ◽  
Self Association ◽  
Associated Species ◽  
Derivatives Of

An analysis of the preferred conformations and modes of self-association of the N-fluoren-9-methoxycarbonyl derivatives of L-alanine and α-aminoisobutyric acid was performed in solution and in the solid state using infrared absorption, 1H nuclear magnetic resonance, and X-ray diffraction. In a solvent of low polarity (deuterochloroform) non-associated and self-associated species (involving predominantly the hydroxyl and carbonyl groups of the carboxylic acid moiety) simultaneously occur. At high dilution, where self-association is absent, the amount of intramolecularly H-bonded forms, if any, should be extremely small. Z(trans) [Formula: see text]E(cis) isomerism about the amide bond of the secondary urethane moiety was observed only for the less bulky L-alanine derivative. In the solid state all H-bonding donors and acceptors of the L-alanine and α-aminoisobutyric acid derivatives take part to complex schemes of intermolecular H-bonds. In the L-alanine derivative, crystallized as monohydrate, most of the intermolecular H-bonds involve the water molecule. Intramolecular H-bonds are not observed in either compound. The conformation about the secondary urethane CO—NH bond is Z(trans) in both compounds. Both L-alanine and α-aminoisobutyric acid residues are partially folded. The observation of the long C(sp3)—O bond of the fluoren-9-yl-methoxycarbonyl moiety might contribute to explain the unexpected experimental result that this protecting group can be removed by catalytic hydrogenation.

scholarly journals Low-temperature infrared study of ammonium carbamate formation

1984 ◽  
Vol 62 (5) ◽  
pp. 945-948 ◽  
Author(s):  
C. Hisatsune
Keyword(s):  
Solid State ◽  
Low Temperature ◽  
Infrared Spectra ◽  
Low Temperatures ◽  
Hydrogen Ion ◽  
Ion Transfer ◽  
Infrared Study ◽  
Ammonium Carbamate

Two types of infrared spectra observed during the formation of ammonium carbamate [Formula: see text] from the reaction of NH3 and CO2 in the solid state at low temperatures have been re-examined. These spectra had been assigned previously to amorphous and crystalline ammonium carbamate but the present data suggest their origins to be [Formula: see text] and its unstable precursor (NH3)2CO2 in which CO2 is bent. Spectra of amorphous and crystalline ammonium carbamate have been distinguished by comparing the systems NH3/CO2 and NH3/CO2/H2O. Hydrogen ion transfer in the diammoniates occurred at about −80 °C for NH3/CO2 and about −40 °C for ND3/CO2.

scholarly journals Low-temperature acidic melts of Bazman volcano (Iran)

2019 ◽  
Vol 485 (5) ◽  
pp. 614-618
Author(s):  
V. Yu. Prokofiev ◽  
V. B. Naumov ◽  
A. E. Roman’ko ◽  
A. L. Balashova ◽  
P. Yu. Plechov ◽  
...  
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Island Arc ◽  
Silicate Melt ◽  
High Concentrations ◽  
Microelemental Composition

The inclusions of a silicate melt were investigated in quartz insets of the extrusive rhyolite collected at Bazman Cenozoic volcano (Iran) and associated with the process of recent subduction. Low temperatures of the silicate melt along with high concentrations of water in the melt are ascertained. The microelemental composition of the melt showed a similarity to acidic melts of island-arc formations.

Magnetic Cooperative Phenomenon with Unpaired sp-Electrons System by MBE Low-Temperature Growth

2019 ◽  
Vol 290 ◽  
pp. 336-341
Author(s):  
Mohd Ambri Mohamed ◽  
Burhanuddin Yeop Majlis
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Molecular Beam ◽  
Electronic Devices ◽  
High Concentration ◽  
Temperature Growth ◽  
Cooperative Phenomenon ◽  
High Concentrations ◽  
Cooperative Transition ◽  
Synthesis Of Materials

We present a new possibility of crystal growth as synthesis of materials containing high concentrations of unpaired sp electrons by growth of Be doped Gallium Arsenides at low temperatures of 200-3000C using Molecular Beam Epitaxy (MBE) and investigate a possibility of applications of magnetotransport properties based on these unpaired sp-electrons to spintronics devices.The present study using high concentration of unpaired sp-electrons by the growth of Beryllium-doped GaAs layers at low temperatures resulted in a cooperative transition of localized spins at low temperature and also affected the mechasnism of tranport properties of the sample from hopping conduction to valence band conduction.This attempts will give rise to a possibility of adding new functions to existing electronic devices.

A Low Temperature Infrared Study on the Association of Thiols with Organic Oxygen Bases

1974 ◽  
Vol 52 (5) ◽  
pp. 738-743 ◽  
Author(s):  
R. Bicca De Alencastro
Keyword(s):  
Low Temperature ◽  
Infrared Spectra ◽  
Infrared Study ◽  
Text Type ◽  
Organic Bases

The infrared spectra of mixtures of propane-1-thiol and several oxygen-containing weak organic bases have been measured between 2500 and 2650 cm−1, in a 1:1 mixture of CCl3F and C2F4Br2 at temperatures ranging from 20 to –190 °C. Association of the [Formula: see text] type was observed between propane-1-thiol and 2-methyl-tetrahydrofuran, or cyclopentanone. This association is less important between the thiol and hexachloropropanone. In the case of a thiol–furan mixture association of the [Formula: see text] type is strongly indicated.

A Low Temperature Infrared Study of Hydrogen Bonding in N-Alkylacetamides

1973 ◽  
Vol 51 (21) ◽  
pp. 3640-3646 ◽  
Author(s):  
Marie-Claude Bernard-Houplain ◽  
C. Sandorfy
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Low Temperature ◽  
Infrared Spectra ◽  
Bond Formation ◽  
Coupling Constant ◽  
Infrared Study ◽  
Hydrogen Bond Formation ◽  
Stretching Vibration ◽  
Secondary Amides

The infrared spectra of N-methylacetamide and two other secondary amides were measured in solution at temperatures ranging from 22 to −190 °C in both the fundamental and the overtone regions. At least two hydrogen bonded species are found as association increases with decreasing temperature. The effect of hydrogen bond formation on the anharmonicity of the NH stretching vibration and on the NH stretching – NH bending coupling constant is examined.

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