scholarly journals The magnetic and optical properties of the benzene ring in aromatic compounds

1929 ◽  
Vol 126 (800) ◽  
pp. 143-154 ◽  
Keyword(s):  
Crystal Lattice ◽  
Benzene Ring ◽  
Unit Cell ◽  
Organic Crystals ◽  
Parallel Plates ◽  
X Ray ◽  
Suitable Material ◽  
Starting Point ◽  
Sufficient Precision ◽  
Complete Interpretation

The present paper describes the third of a series of investigations undertaken at the suggestion of Sir C. V. Raman of the remarkable magnetic and optical characters exhibited by organic crystals of the aromatic class. In the earlier papers the author had described the optical and the magnetic characters of naphthalene crystals and also of anthracene and other organic compounds and discussed the significance of the results. In all these cases, however, the fact that there were two or more molecules per unit cell in the crystal lattice, and that the X-ray results available did not fix with sufficient precision either the form of the molecules or their orientation relatively to each other and to the crystal lattice prevented a complete interpretation of the results. Mrs. Lonsdale’s recent admirable investigation of the structure of hexamethylbenzene has made further and very significant progress possible. She has shown that this substance crystallises in the triclinic system with one molecule per unit cell and that the carbon atoms in the molecule form flat hexagonal rings parallel to a cleavage plane. Hence this substance forms a very suitable material for the experimental study of the magnetic and optical characters of the benzene ring in its substitution products. It has accordingly been used as the starting point in the present investigation. For convenience of reference Mrs. Lonsdale's results will be briefly recalled here. The nomenclature adopted is the same as hers. The substance crystallises out of benzene mostly in parallel plates with the be plane prominently developed. Often there are two other pairs of faces, fairly well developed, which were chosen by her as the ab and ac planes. The unit cell thus defined is a triclinic cell which was found to have the following axes and axial angles:— A. U. ° ˊ 9.010 . . . . . . . . . . . . . . . . . 44 27 8.926 . . . . . . . . . . . . . . . . . 116 43 5.344 . . . . . . . . . . . . . . . . . 119 34 The crystal is centrosymmentrical with one molecule per cell.

scholarly journals IX—investigations on magne-crystallic action III—Further studies on organic crystals

1935 ◽  
Vol 234 (739) ◽  
pp. 265-298 ◽  
Keyword(s):  
Molecular Structure ◽  
Crystal Lattice ◽  
Convenient Method ◽  
Organic Crystals ◽  
Double Refraction ◽  
Magnetic Susceptibilities ◽  
X Ray ◽  
Benzene Rings ◽  
The Individual ◽  
Ray Methods

In Part I* of this paper a convenient method of measuring the principal magnetic susceptibilities of single crystals was described, and several organic crystals, among others, were studied by this method. The results were discussed particularly in relation to the structure of the molecules and their orientations in the crystal lattice, and it was shown how a correlation of the principal magnetic susceptibilities of the crystal with those for the individual molecules (obtained from measurements on magnetic double-refraction in the liquid state, or from considerations of molecular structure) gives us useful information regarding the orientations of the molecules in the crystal lattice. Indeed, in favourable cases the molecular orientations may thus be determined much more easily, and some of the parameters defining the orientations also more accurately, than by X-ray methods of analysis. Conversely, where the molecular orientations in the crystal lattice are already known from X-ray studies, a knowledge of the principal magnetic susceptibilities of the crystal enables us to obtain the magnetic constants of the individual molecules, which are of interest. For example, it is thus found that as one proceeds from benzene to naphthalene and from naphthalene to anthracene, the numerical increase in susceptibility that occurs, is directed predominantly along the normal to the plane of the benzene rings

Synthesis and X-ray diffraction study of calcium salts of some carboxylic acids

2002 ◽  
Vol 17 (1) ◽  
pp. 13-18 ◽  
Author(s):  
A. Valor ◽  
E. Reguera ◽  
F. Sa´nchez-Sinencio
Keyword(s):  
Carboxylic Acids ◽  
Unit Cell ◽  
Calcium Stearate ◽  
Aliphatic Chain ◽  
X Ray Diffraction ◽  
Calcium Salts ◽  
Calculated Density ◽  
X Ray ◽  
Cell Parameters ◽  
Starting Point

An experimental X-ray diffraction (XRD) study of calcium salts of four carboxylic acids is presented. Calcium salts of propionic, butyric, valeric, and caproic acids were synthesized mixing in a mortar Ca(OH)2 with the liquid acids. Measuring the thermogravimetric analysis curves it was determined that the salts were actually monohydrates. The densities of the synthesized samples were measured using a density gradient column. The measured values for the densities were as follows: Dm(propionate)=1.38 g/cm3, Dm(butyrate)=1.30 g/cm3, Dm(valerate)=1.26 g/cm3, Dm(caproate)=1.22 g/cm3. The XRD analysis revealed that these compounds have monoclinic cells with symmetry described by the P21/a space group. Calcium propionate hydrate has cell parameters: a=2.437 51(5) nm, b=0.681 24(1) nm, c=0.591 43(1) nm, β=95.320(2)°. For calcium butyrate hydrate the cell parameters are: a=2.966 84(8) nm, b=0.680 74(2) nm, c=0.589 29(2) nm, β=95.442(3)°. The cell parameters for calcium valerate hydrate are: a=3.566 36(4) nm, b=0.682 49(1) nm, c=0.592 77(1) nm, β=107.280(1)° and for calcium caproate hydrate a=4.180 30(5) nm, b=0.682 61(1) nm, c=0.592 13(1) nm, β=110.230(1)°. The calculated density values from the XRD results, taking into account that the number of chemical formulas in the unit cell equals four, agree very well with the measured ones. It was established that the unit cell parameter a grows with the increase of the number of carbon atoms in the aliphatic chain, while parameters b and c remain almost constant. This is an indication of the stacking layer character of the structure as has been suggested for calcium stearate monohydrate. This fact points to the possibility of the refinement of the crystalline structures taking as the starting point the reported structure for calcium stearate monohydrate.

scholarly journals Single Crystal X-ray Diffraction, Spectroscopic and Mass Spectrometric Studies of Furanocoumarin Peucedanin

2014 ◽  
Vol 9 (1) ◽  
pp. 1934578X1400900
Author(s):  
Magdalena Bartnik ◽  
Marta Arczewska ◽  
Anna A. Hoser ◽  
Tomasz Mroczek ◽  
Daniel M. Kamiński ◽  
...  
Keyword(s):  
Single Crystal ◽  
Crystal Lattice ◽  
2D Nmr ◽  
Unit Cell ◽  
Spectroscopic Techniques ◽  
Fragmentation Pattern ◽  
X Ray Diffraction ◽  
X Ray ◽  
Single Column ◽  
Biological Tests

The structure of peucedanin, isolated from Peucedanum tauricum Bieb. (Apiaceae), has been established using single crystal X-ray diffraction. This furanocoumarin isolated from the light petroleum extract of P. tauricum fruits was characterized by high resolution EI-MS, sATR-FTIR and 2D NMR spectroscopic techniques. The EI-MS showed the typical fragmentation pattern of methoxyfuranocoumarins. Extensive 1D (1H and 13C) as well as 2D NMR data enabled complete assignment of the carbon atoms in the peucedanin molecule. The FTIR data confirms intermolecular hydrogen bonding between peucedanin molecules in polar solvents. Peucedanin crystallises in the R-3 space group from the trigonal system with one molecule in the asymmetric part of the unit cell. The crystal lattice of peucedanin consists of the molecules arranged in separate columns. They are related by two fold screw axes and centres of symmetry. Interestingly, peucedanin columns form two channels per unit cell with a diameter of 7.5Å going through the crystal lattice in the Z-direction. These channels are filled with disordered water molecules, which are surrounded by hydrophobic methyl groups and are located exactly at the centres of the channels. The peucedanin molecules are stacked in a single column with the opposite orientation of the neighbouring molecules. These results could be interesting in further application of this molecule, for example in biological tests of its activity.

scholarly journals Oscillatory Changes in Structural Characteristics in Multicomponent Ceramics, YBCO

2022 ◽  
Author(s):  
B. Kodess
Keyword(s):  
Phase Composition ◽  
Crystal Lattice ◽  
Structural Characteristics ◽  
Oscillatory Behavior ◽  
Unit Cell Dimension ◽  
Unit Cell ◽  
Specific Process ◽  
X Ray ◽  
Compression And Expansion ◽  
Long Time

Abstract. The structural characteristics of samples of a four-component superconducting material (YBCO) after exposure to X-ray irradiation during a long time are investigated. The effect of X-ray beam processing on angular positions (corresponding parameters of the crystal lattice) and the width of Bragg reflections is established. The phenomenon of oscillatory behavior in the unit cell dimension with long-time irradiation is found. The analysis of the profiles of reflection also demonstrates the presence of reversible changes phase composition with the exposure time. The observed phenomena reflect the presence of a nontrivial and specific process of compression and expansion of the unit cell due to the accumulation and then disengagement outside of ionized oxygen, which is formed under such irradiation exposure on the surface of the samples.

scholarly journals Synthesis, spectroscopic studies and X-ray structure determination of two mononuclear copper complexes derived from the Schiff base ligand N,N-dimethyl-N'-((5-methyl-1H-imidazol-4-yl)methylene)ethane-1,2-diamine

2019 ◽  
Vol 10 (3) ◽  
pp. 201-208
Author(s):  
Pokpa Haba ◽  
Adama Sy ◽  
Farba Bouyagui Tamboura ◽  
Mamour Sarr ◽  
Ibrahima Elhadji Thiam ◽  
...  
Keyword(s):  
Schiff Base ◽  
Crystal Lattice ◽  
Structure Determination ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

Reactions of the Schiff base N,N-dimethyl-N'-((5-methyl-1H-imidazol-4-yl)methylene) ethane-1,2-diamine (HL), synthesised in situ, with chloride or thiocyanate copper (II) salt; afforded two new mononuclear complexes, [Cu(HL)Cl2]·H2O (1) and [Cu(HL)(SCN)2] (2). These compounds have been studied and characterized by elemental analysis, IR and UV-Vis spectroscopies, electrochemistry, molar conductivity and room temperature magnetic measurements. Single crystal X-ray structure determination of the complexes revealed the presence of neutral moieties in the asymmetric unit. The mononuclear (1) crystallises in the monoclinic space group P21/c with the following unit cell parameters a = 7.4355(3) Å, b = 7.2952(3) Å, c = 26.2729(11) Å, β = 93.461(4)°, V = 1422.52(10) Å3, Z = 4, R1 = 0.033 and wR2 = 0.082 and the mononuclear complex (2) crystallises in the monoclinic space group C2/c with the following unit cell parameters a = 26.2578(7) Å, b = 7.4334(2) Å, c = 16.6237(5) Å, β = 99.089(3)°, V = 3203.95(16) Å3, Z = 8, R1 = 0.037 and wR2 = 0.104. In both complexes the ligand acts in tridentate fashion and the coordination environment of the copper atom can be described as distorted square pyramidal. The crystal lattice of the complex 1 is stabilized by electrostatic forces of attraction and O–H···Cl, C–H···O, N–H···Cl, and C–H···Cl, hydrogen bonding interactions while the crystal lattice of the complex 2 is stabilized by N–H···S and C–H···N.

scholarly journals SYNTHESIS AND X-RAY INVESTIGATION OF Cu2CdSn(SxSe1–x)4 SOLID SOLUTIONS

2018 ◽  
Vol 54 (2) ◽  
pp. 229-233
Author(s):  
A. U. Sheleg ◽  
V. F. Gremenok ◽  
A. S. Sereda ◽  
V. G. Hurtavy ◽  
V. A. Chumak ◽  
...  
Keyword(s):  
Crystal Lattice ◽  
Solid Solutions ◽  
Profile Analysis ◽  
Rietveld Method ◽  
Diffraction Method ◽  
Unit Cell ◽  
Continuous Series ◽  
Unit Cell Parameters ◽  
X Ray ◽  
Cell Parameters

The quaternary semiconductors Cu2CdSnS4, Cu2CdSnSe4 and Cu2CdSn(SxSe1–x)4 solid solutions were synthesized by the one-temperature method from the elementary components. The X-ray diffraction method showed that the obtained polycrystalline samples are single-phased. The unit cell parameters of the synthesized compounds and Cu2CdSn(SxSe1–x)4 solid solutions were determined from diffraction spectra by the full-profile analysis using the Rietveld method with the Fullprof software package. It has been established that with an increase in sulfur concentration, the unit cell parameters decrease smoothly linearly in accordance with the Vegard rule, which indicates the formation of a continuous series of solid solutions in the Cu2CdSn(SxSe1–x)4 system within the range 0 ≤ x ≤ 1. The parameter of crystal lattice tetragonal distortions h of the investigated compounds is calculated. The h values are close to 1 for all the compositions studied, which indicates a small crystal lattice distortion of the obtained samples.

scholarly journals The crystalline structure of naphthalene. A quantitative X-ray investigation

1933 ◽  
Vol 142 (847) ◽  
pp. 674-688 ◽  
Keyword(s):  
Melting Point ◽  
Single Crystal ◽  
Unit Cell ◽  
Molecular Volume ◽  
Experimental Measurements ◽  
Organic Crystals ◽  
Molecular Symmetry ◽  
Crystal Data ◽  
X Ray ◽  
Small Single Crystal

Crystal Data . Naphthalene .—C 10 H 8 . Melting point 80° C. Density 1·152 (calc. 1·172). Monoclinic prismatic, a = 8·29, b = 5·97, c = 8·68 A., β = 122·7°. Space group C 2λ 5 (P2 1 / a ). Two molecules per unit cell. Molecular symmetry, centre. Molecular volume, 362 A 3 . Total number of electrons per unit cell = F(000) = 136. Experimental—Measurements of Intensities . When a small single crystal is placed completely in an X-ray beam, the integrated reflection is proportional to the mass of the crystal, if the latter is sufficiently small. Although fairly large crystals of naphthalene can easily be obtained, the aim in this work has been to carry out the measurements on specimens small enough for this proportionality to hold good. With soft, organic crystals of the hydrocarbon type, the size required for reliable results is found to be of order of 0·1 milligrams.

The External Shape of Human γ GI Immunoglobulin from Crystal Sections

1971 ◽  
Vol 29 ◽  
pp. 428-429
Author(s):  
L. W. Labaw
Keyword(s):  
Molecular Weight ◽  
Sodium Phosphate ◽  
Osmium Tetroxide ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
X Ray ◽  
Large Molecular Weight ◽  
Cell Dimensions ◽  
Unit Cell Dimensions ◽  
Crystallographic Axes

Crystals of a human γGl immunoglobulin have the external morphology of diamond shaped prisms. X-ray studies have shown them to be monoclinic, space group C2, with 2 molecules per unit cell. The unit cell dimensions are a = 194.1, b = 91.7, c = 51.6Å, 8 = 102°. The relatively large molecular weight of 151,000 and these unit cell dimensions made this a promising crystal to study in the EM.Crystals similar to those used in the x-ray studies were fixed at 5°C for three weeks in a solution of mother liquor containing 5 x 10-5M sodium phosphate, pH 7.0, and 0.03% glutaraldehyde. They were postfixed with 1% osmium tetroxide for 15 min. and embedded in Maraglas the usual way. Sections were cut perpendicular to the three crystallographic axes. Such a section cut with its plane perpendicular to the z direction is shown in Fig. 1.This projection of the crystal in the z direction shows periodicities in at least four different directions but these are only seen clearly by sighting obliquely along the micrograph.

X-ray Structure Refinement and Vibrational Spectroscopy of Ca8Gd2 (PO4)6 O2

2013 ◽  
Vol 12 (10) ◽  
pp. 719-726
Author(s):  
R. Ayadi ◽  
Mohamed Boujelbene ◽  
T. Mhiri
Keyword(s):  
Solid State ◽  
General Formula ◽  
Vibrational Spectroscopy ◽  
Powder Diffraction ◽  
Infrared Spectra ◽  
Solid State Reaction ◽  
Structure Refinement ◽  
Unit Cell ◽  
Cell Group ◽  
X Ray

The present paper is interested in the study of compounds from the apatite family with the general formula Ca10 (PO4)6A2. It particularly brings to light the exploitation of the distinctive stereochemistries of two Ca positions in apatite. In fact, Gd-Bearing oxyapatiteCa8 Gd2 (PO4)6O2 has been synthesized by solid state reaction and characterized by X-ray powder diffraction. The site occupancies of substituents is0.3333 in Gd and 0.3333 for Ca in the Ca(1) position and 0. 5 for Gd in the Ca (2) position.  Besides, the observed frequencies in the Raman and infrared spectra were explained and discussed on the basis of unit-cell group analyses.

Fabrication and study the effect of the laser on the properties of the compound Tl2-xHgxBa2-ySryCa2Cu3O10+δ superconductor

2018 ◽  
pp. 168
Author(s):  
A. Kareem Dahash Ali ◽  
Nihad Ali Shafeek
Keyword(s):  
Transition Temperature ◽  
Solid State ◽  
Hydrostatic Pressure ◽  
Electrical Properties ◽  
Co2 Laser ◽  
Temperature Shift ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural And Electrical Properties

This study included the fabrication of    compound (Tl2-xHgxBa2-ySryCa2Cu3O10+δ) in a manner solid state and under hydrostatic pressure ( 8 ton/cm2) and temperature annealing(850°C), and determine the effect of the laser on the structural and electrical properties elements in the compound, and various concentrations of x where (x= 0.1,0.2,0.3 ). Observed by testing the XRD The best ratio of compensation for x is 0.2 as the value of a = b = 5.3899 (A °), c = 36.21 (A °) show that the installation of four-wheel-based type and that the best temperature shift is TC= 142 K  .When you shine a CO2 laser on the models in order to recognize the effect of the laser on these models showed the study of X-ray diffraction of these samples when preparing models with different concentrations of the values ​​of x, the best ratio of compensation is 0.2 which showed an increase in the values ​​of the dimensions of the unit cell a=b = 5.3929 (A °), c = 36.238 (A°). And the best transition temperature after shedding laser is TC=144 K. 

Sign in / Sign up

Export Citation Format

Share Document