Wyniki wyszukiwania - Biblioteka Nauki

1

The Crystal and Molecular Structure of 1-Methyl-4-(p-methybenzylidene)-2-methylseleno-5-imidazolinone

100%

Żesławska E. , Oleksyn B. , Korohoda M. , Śliwiński J.

Polish Journal of Chemistry

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2000

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tom Vol. 74, nr 6

751-757

EN

The crystal structure of 1-ethyl-4-(p-methylbenzylidene)-2-methylseleno-5-imidazolinone has been determined by X-ray diffraction methods. The crystals are triclini, space group P1, with a=8.130 (1) A, b=8.888(1) A, c=9.287(1) A, alpha=93.80(1)o, beta=94.86(1)o, gamma=92.67(1)o, Z=2. The molecule is approximately planar with most of the bonds participating in a conjugated system, stabilized by weak intramolecular hydrogen bond, C8-H8 ...N1. Concusions about electron distribution within this system have been drawn from the bond angles and bond lenghts. In the unit cell, molecular pairs can be discrened with antiparallel imidazole rings in the distance of 3.5 A.

2

Comparison of the molecular structures of 1,5-bis(p-toluenesulphonamido)-2,4,6,8-tetranitronaphthalene and its dianion in the bispyridinium salt

100%

Olejnik Z. , Lis T. , Grech E. , Nowicka-Scheibe J.

Polish Journal of Chemistry

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1998

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tom Vol. 72, nr 7

1255-1268

EN

1,5-Bis(p-toluenesulphonamido)-2,4,6.8-tetranitronaphthalene (1,5-TSATNN) [alternative name: N,N'-(2,4,6,8-tetranitronaphthalene-1,5-diyl)-bis(p-toluenesulphonamide)] crystalized from acetic acid or pyridine with three molar equivalents of solvent. The compound with pyridine is shown to be a 1:1 adduct of bispyridinium salt. Substantial differences between molecular geometries of 1,5-TSATNN and its dianion are found. Naphthalene cores are distorted from planarity in quite different modes and the neutral and deprotonated p-tosylamide groups adopt different rotational conformations. A significant delocalization of the negative charge, observed as shortening of the S-N and N(amide)-C bonds, as well as evidence of conjugation between the amide and nitro groups are found in the dianion.

3

Assessment of Detonation Performance and Characteristics of 2,4,6-Trinitrotoluene Based Melt Cast Explosives Containing Aluminum by Laser Induced Breakdown Spectroscopy

100%

Rezaei A. H. , Keshavarz M. H. , Tehrani M. K. , Darbani M. R.

Central European Journal of Energetic Materials

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2019

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tom Vol. 16, no. 1

3--20

EN

Aluminized melt cast formulations based on 2,4,6-trinitrotoluene (TNT) deliver an enhanced blast effect because the secondary combustion process of aluminum (Al) occurs beyond the detonation zone. A new method is introduced to assess the detonation performance and characteristics of aluminized TNT explosives on the basis of the laser-induced breakdown spectroscopy (LIBS) technique, in both air and argon (Ar) atmospheres. The plasma emissions of the prepared samples were recorded, where the atomic lines of Al, C, O and H as well as the molecular bands of AlO, CN and C2 were identified. A good discrimination and separation between the samples was possible using LIBS and principle component analysis (PCA), although they had similar atomic compositions. The quantitative calibration curve obtained using the relative intensity of Al/O was used to determine the detonation velocity/pressure and aluminum content of the TNT/Al samples. Comparisons between experimental and theoretical spectra were made using a Nelder–Mead temperature program for CN bands, which provided good agreement with the fitted spectra. Finally, CN vibrational temperatures were calculated from these spectral fittings. These temperatures have higher values in an Ar atmosphere than in an air atmosphere. Thus, increasing the oxygen concentration can decrease these temperatures in TNT/Al standard samples.

4

Crystal and molecular structure of 3B-acetoxy-21-(2-hydroxy-2methylopropoxy)-cholest-5-en-25-ol, the first "double side chain" choresterol analogue investigated by X-ray diffraction

100%

Gałdecka E. , Gałdecki Z. , Górkiewicz Z. , Kurek-Tyrlik A. , Makaev F. , Wicha J. , Calverley M.

Polish Journal of Chemistry

|

1999

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tom vol. 73 nr 3

541-555

EN

The title steroid crystallizes in the monoclinic P21 space group with unit cell dimensions: a=11.745(2) A, b=10.564(2) A, c=12.979(3) A, b = 95.73(3)0. Its crystal and molecular structure was determined by X-ray diffraction methods. The A ring has a symmetrical chair conformation. The B ring has a half-chair conformation, with asymmetry parameter D5,62=0.60. The C ring has an intermediate sofa-half-chair conformation with asymmetry parameters: DC9s=2.30, DC11s=5.80, DC9,112=4.80, and DC8,92=5.60. The D ring adopts an envelope conformation with asymmetry parameter DC13s=10.70. The cholesterol side chain adopts a fully extended conformation with torsion angles -170.6(6)0, 167.9(6)0 , -171.9(6)0 , and 175.6(7)0 , i.e. it belongs to the most populated conformer A, and with the terminal C26 and C27 methyl groups in gauche, trans conformations.

5

Molecular structure of 5-chloro-2-[p-t-butylphenyl]benzoxazole : Relation between structure and antimicrobial activity of 2,5-disubstituted benzoxazoles

100%

Mrozek A. , Trzeźwińska H. , Karolak-Wojciechowska J.

Polish Journal of Chemistry

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1999

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tom vol. 73 nr 4

625-633

EN

As part of our investigation on antimicrobial agents, the structure of 5-chloro-2[p-t-butylophenyl]benzoxazole is reported: C17h16ClNO, mol.mass 285.77, monoclinic, space group: C2/c; a=32.164(6) A, b=6.756(1) A, c=13.710(3) A; b=92.73(3)0, V=2975.8(10) A3; d=1.276 g cm-3; Z=8; F(000)=1200; m(CuKa)=2.219 mm-1. Final R=0.0658 for 2621 reflections with F>4s(F). Final atomic coordinates for this 2,5-disubstitued benzoxazole were used as a starting point in molecular modeling of remaining 32 derivatives eearched as antimicrobial agents. Electronic parameters calculated with quantum chemistry methods and classical Hansch's constants were applied in searching for structure-activity correlation. It was established that geometrical parameters (area and volume) and LUMO energy values seem to be most important for the activity.

6

X-ray investigations of four selected multifunctional phenylsulfones

100%

Gałdecka E. , Gałdecki Z.

Polish Journal of Chemistry

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1999

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tom vol. 73 nr 5

821-843

EN

The crystal and molecular structures of following selected multifunctional phenylsulfones were determined by X-ray diffraction methods using an Enraf-Nonius CAD4S diffractometer: a-(4-biphenylsulfonyl)acetophenone, (1); a-methyl-a-[4-(acetylamino)phenylsulfonyl]acetophenone, (II); 1,1-dichloro-2-phenyl-2-(4-allylsulfonylphenyl)ethane, (III); 1,1-dichloro-2-phenyl-2-(4-chlorosulfonylphenyl)ethane, (IV). The compound (I), (C20H16O3S), crystallizes in the monoclinic P21/c space group with unit cell dimensions: a =9.0527(6) A, b = 5.333(1) A, c= 34.286(2) A, b = 94.796(5)0. Analyzis of benzene-ring geometry leads to the conclusion that the bond angles and distances within the benzene rings of the four investigated structures seem normal, and only small deviations occur. In (I) all three rings are almost planar and the two rings the biphenyl are almost coplanar. The compound (II), (C17H17NO4S), crystallizes in the monoclinic P21/c space group with unit cell dimensions: a = 10.943(4) A, b = 8.566(2) A, c= 17.286(4) A, b = 90.57(3)0. Both rings are almost planar. The compound (III), (C17H14O2SCl2), crystallizes in the monoclinic P21/c space group with unit cell dimensions: a = 12.577(20) A, b = 18.961(2) A, c= 7.407(2) A, b = 103.83(2)0. Both rings are almost planar - the dihedral angles in ring A vary from -1.7o to 1.2o, and in ring B from -1,7o to 1,6o. The planes of the two rings are nearly perpendicular to each other.

7

Crystal and Molecular Structure of (-)-(S)- and (+)-(R)-Bromofosfamide

100%

Karolak-Wojciechowska J. , Wieczorek M. , Grynkiewicz G. , Kutner A.

Polish Journal of Chemistry

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1999

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tom Vol. 73, nr 11

1877-1885

EN

The crystal and molecular structures of (-)-(S)- and (+)-(R)-bromofosfamide were determined as a part of our research on therapeutically useful oxazaphosphorines. Both compounds crystallized in strictly enantiotropic crystals. Both sompound undergo partial decomposition during diffractometric exposition with emission of free bromine.

8

A Novel Correlation for Predicting the Density of Tetrazole–N-oxide Salts as Green Energetic Materials through Their Molecular Structure

88%

Zohari N. , Bajestani I. R.

Central European Journal of Energetic Materials

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2018

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tom Vol. 15, no. 4

629--651

EN

In this study, a new and reliable model is derived for predicting the density of tetrazole N-oxide salts using molecular structure descriptors through multiple linear regression methods (MLR). The proposed model is based on the elemental, functional group and type of molecule descriptors. The coefficient of determination (R2) of the model was 0.9321 for 36 energetic tetrazole N-oxides with different molecular structures as an exploratoryset. The predictive ability of this model has been checked using a cross validation method (Q2 LOO = 0.9325 and Q2 LMO = 0.9324). The new correlation had a root mean square deviation (RMSD) of 0.033 g·cm−3 and an average absolute deviation (AAD) of 0.025 g·cm−3. This correlation also gave good predicted results for a further 10 energetic tetrazole N-oxides as a test set. The new reliable model can also be appliedfor designing novel energetic tetrazole N-oxides.

9

A Simple Approach for Predicting the Density of High Nitrogen Organic Compounds as Materials for Providing Clean Products and Enormous Energy Release

88%

Keshavarz M. , Ebadpour R. , Jafari M.

Central European Journal of Energetic Materials

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2020

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tom Vol. 17, no. 2

296--317

EN

High nitrogen organic compounds (N>50 wt.%) are important for chemical industries because they can provide clean products with generally low-molecular weight product gases and enormous energy release. The density of these materials at or near room temperature is an important physical property for the assessment of their detonation and combustion performances. A novel method is introduced here for the prediction of the density of various classes of organic compounds, including different derivatives of triazole, tetrazole, triazine, tetrazine, furazan, and some organic nitrogen-containing chains. The core model is based on elemental composition, where its reliability has been improved by considering some molecular fragments including specific functional groups. The high reliability of these simple model has been compared with the output from two complex quantum mechanical approaches. For 91 high nitrogen compounds, the values of the standard deviation (SD) of the core and improved correlations were 0.076 and 0.047 g·cm–3. For a further 32 materials, the values of SD were 0.057 and 0.042 g·cm–3 for the core and improved correlations, respectively. These data are close to core and improved quantum mechanical methods, i.e. 0.056 and 0.042 g·cm–3, respectively, where the calculated data from complex quantum mechanical approaches were available.

10

Surface properties of some carotenoids spread in monolayers at the air/water interface. Experimental and computational approach

88%

Horovitz O. , Tomoaia G. , Racz C. , Mocanu A. , Bobos L.-D. , Tomoaia-Cotisel M.

Open Chemistry

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2006

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tom 4

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nr 3

489-501

EN

The surface pressure versus molecular area isotherms of some carotenoids: β,β-carotene-4-one (echinenone, ECH), β,β-carotene-4,4′-dione (canthaxanthin, CAN) and 4,4′-diapo-ω,ω-carotene-4,4′-dial (APO), spread at the air/water interface, are reported. A van der Waals type state equation is used to describe the high molecular area portions of the compression isotherms and interaction parameters within monolayers are derived. Quantum chemical semi-empirical SCF MO calculations (AM1 and PM3) are performed for the optimized geometries of molecules and dipole moments are calculated. Similar theoretical magnitudes are obtained by both methods. Surface properties, like collapse pressure, surface compressional modulus and interaction parameters are discussed in terms of dipole-dipole interactions, and correlations with the calculated quantities for the carotenoid molecules are analyzed. The orientation of the different carotenoid molecules in the monolayer is discussed.

11

The factor VIII protein and its function

88%

Mazurkiewicz-Pisarek A. , Płucienniczak G. , Ciach T. , Płucienniczak A.

Acta Biochimica Polonica

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2016

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tom 63

|

nr 1

11-16

EN

Factor VIII (FVIII), an essential blood coagulation protein, is a key component of the fluid phase blood coagulation system. Human factor VIII is a single chain of about 300 kDa consisting of domains described as A1-A2-B-A3-C1-C2. The protein undergoes processing prior to secretion into blood resulting in a heavy chain of 200 kDa (A1-A2-B) and a light chain of 80 kDa (A3-C1-C2) linked by metal ions. The role of factor VIII is to increase the catalytic efficiency of factor IXa in the activation of factor X. Variants of these factors lead frequently also to severe bleeding disorders.

12

Angular overlap treatment of cis-bis(2,2'-bipyridyl)dichlorochromium(III) chloride dihydrate in aqueous solution

88%

Kurzak K. , Biernacki K.

Polish Journal of Chemistry

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1998

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tom Vol. 72, nr 4

660-666

EN

Six-coordinate cis-[CrCL2(bipy)2](+) complex (bipy=2,2'-bipyridyl) has been prepared. Electron spectrum of aqueous solution of this complex has been recorded and explained by the angular overlap model (AOM), assuming C-2v symmetry. All transition energies are derived from Gaussian analysis of the spectrum. The calculations of the ligand field parameters take into account all the transitions required in the ligand field (LF) theory (except those energetically higher than the range of the spectrum recorded).

13

Thin films of copper phthalocyanine deposited by solution processing methods

88%

Gojzewski H. , Ghani F. , Szybowicz M.

Materials Science Poland

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2020

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tom Vol. 38, No. 1

79--90

EN

In this work, we show and discuss the surface structure picture of copper phthalocyanine (CuPc) thin films deposited from trifluoroacetic acid (TFA) solvent onto silicon substrates at ambient conditions by four solution processing methods, namely drop-casting, dip-coating, spin-casting and spray-coating. The CuPc films were studied by AFM, as the main technique, and complemented by micro-Raman spectroscopy. Essentially, such thin films consist of CuPc molecular nanoribbons of a fixed ~1 nm thickness. CuPc molecules are arranged in an in-plane direction and formed in stacks under a defined tilt angle with respect to the substrate surface (monolayer) or underlying CuPc layer (multilayer). The film morphology takes various forms depending on the solution concentration, number of layers, and the deposition method. For instance, the morphology varies from very wide (~600 nm) but flat (~1 nm) ribbons for films prepared by dip-coating to crystallized rod-like features (multi-layered ribbons) when obtained by spray-coating. The factors studied in this paper should be taken into consideration in designing and controlling the criteria for rigorous CuPc film architecture.

14

Assessment of the Thermal Decomposition Temperature of High-Energy Heterocyclic Aromatic Compounds in Order to Increase Their Safety during Storage, Handling and Application

88%

Keshavarz M. H. , Mousavi S. , Drikvand M.

Central European Journal of Energetic Materials

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2022

|

tom Vol. 19, no. 1

39--62

EN

Heterocyclic aromatic compounds containing various derivatives of five or six-membered nitrogen-containing rings, viz. triazoles, tetrazoles, furazans, triazines, and tetrazines, and some of their salts have been studied. High nitrogen content and a large positive heat of formation are two important properties of these compounds. Two new models are introduced for the reliable prediction of the thermal stability of these compounds through the thermal decomposition temperature (onset). The reported data for 181 compounds have been used to derive and test the new models. For a training set containing 132 heterocyclic aromatic compounds, the values of the average absolute deviation (AAD) and the coefficient of determination (R2) of the improved correlation were 9.72 K and 0.959, respectively. For triazoles, tetrazoles, furazans, triazines, and tetrazines, the predicted results of ADD and R2 for the external test data set for this model containing 41 compounds were 23.03 K and 0.664, respectively, which are closer to experimental data than those obtained by the core correlation, i.e. 26.49 K and 0.653, respectively. The correlation coefficients of cross-validation for leave-one-out (Q2LOO) and 5-fold (Q25CV) of the improved correlation were 0.955 and 0.951, respectively, which confirm that it is not an over-fitted model, robust and well-behaved.

15

Crystal and molecular structures of three anxiolytic pyrazolopyridines

88%

Kubicki M. , Codding P.

Polish Journal of Chemistry

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1999

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tom vol. 73 nr 4

693-706

EN

The crystal structures of three pyrazolopyridines, ethyl 4-amino-6-ethyl-1-pentyl-1H-pyrazolo[3,4-b]pyridinum-5-oate chloride hydrate C16H25N4O2+ × Cl- (2), and 4-amino-1-pentyl-1H-pyrazolo[3,4-b]pyridine-5-N-(2-propenyl)carboxamide C15H21N5O (3) have been determined by X-ray structure analysis of single crystals. The ethyl and isopropyl substituents in compounds 1 and 2, respectively, which are in ortho position relative to the ester group, cause a twist of the O=C-O-C plane with respect to the plane of pyrazolopyridine ring system. In the absence of that steric hindrance, in compound 3, the intramolecular N(amine)-H…O hydrogen bond closes the nearly planar six-membered ring. The coplanarity of the ester or amide plane with the plane of ring system is probably a necessary condition for the significant anxiolytic action. In both cations, the protonation takes place at the pyridine nitrogen atom. In the crystal structures of salts there are separate layers of anions and cations. In the free base, intermolecular hydrogen bonds make infinite chains of molecules.

16

Intermediates in the von Pechmann Reaction

88%

Nowakowska E. M. , Zaleski J. , Kyzio J. B.

Polish Journal of Chemistry

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2008

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tom Vol. 82, nr 7

1399-1399

EN

Condensation of meta-cresol with ethyl acetoacetate in dehydrated phosphoric acid is slow enough to observe formation and disappearance of the in termediates viz 1,2- di -hydro-4,7-dimethyl-4-(4-hydroxy-2-methylphenyl)-coumarin (3) and 1,2- di hydro- 4,7-dimethyl-4-(2-hydroxy-4-methylphenyl)-coumarin (4). GCMS analyses of the reaction mixtures indicated that 4,7-dimethylcoumarin (5) was formed from 3 and 4 by elimination of meta-cresol molecule. The compounds 3 and 4 were isolated by the column chromatography. Their structures were elucidated by the spectroscopic methods but unequivocal assignment of the structure to the particular isomer was not possible. The structures were resolved by X-ray diffraction studies.

17

Development of starch granule molecular and supramolecular structure

88%

Hedley C. , Bogracheva T.

Polish Journal of Natural Sciences. Supplement

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2003

|

tom 01

18

Badania zależności pomiędzy strukturą chemiczną wybranych związków fenolowych, występujących w surowcach żywnościowych oraz ich soli a ich podatnością na biodegradację

75%

Samsonowicz M. , Matejczyk M. , Troc M.

Aparatura Badawcza i Dydaktyczna

|

2012

|

tom T. 17, nr 4

37-43

PL

W ostatnich latach związki polifenolowe zyskują coraz większe zainteresowanie konsumentów i wytwórców żywności. Wyniki badań epidemiologicznych wskazują na prozdrowotne efekty spożywania żywności bogatej w polifenole przede wszystkim ze względu na ich właściwości przeciwutleniające i przeciwrodnikowe. Do tej grupy związków należą hydroksylowe pochodne kwasu benzoesowego. W pracy przedstawiono badania podatności na biodegradację soli wybranych fenolokwasów, różniących się ilością oraz położeniem grup hydroksylowych w cząsteczce oraz toksyczność ostrą w stosunku do wybranych organizmów wskaźnikowych. Stopień biodegradacji oceniano na podstawie redukcji wskaźników zanieczyszczeń tj. RWO i BZT. Określono strukturę analizowanych związków posługując się metodami spektroskopowymi (UV-VIS, FT-IR) oraz teoretycznymi obliczeniami kwantowo-mechanicznymi.

EN

Nowadays phenols are compounds of an increasing interest of costumers and food producers. Results of epidemiological researches indicate a health promoting effect of eating foods rich in polyphenols, mainly due to their anti-free radicals and antioxidant properties. Hydroxyl derivatives of benzoic acid belong to this group of compounds. In this paper investigations of biodegradability and the acute toxicity toward indicator organisms of selected phenolic acids differing in the number and location of hydroxyl groups in the molecule and their salts were presented. The degree of biodégradation was determined based on reduction of pollution indicators such as DOC and BOD. The molecular structures of studied compounds were determined by spectroscopic method (UV-VIS, FT-IR) and using quantum-mechanical calculations.

19

Betainy jako akceptory protonu

75%

Dega-Szafran Z. , Szafran M.

Wiadomości Chemiczne

|

2017

|

tom [Z] 71, 7-8

609--628

EN

Ammonium alkanoates (ammonioalkanocarboxylates) are zwitterions (or inner salts, or betaines), because they possess formally charged ammonium and carboxylate groups separated by one or more sp3 carbon atoms. The chemistry of betaines has become a subject of particular interest due to their applications in biological research, especially with regard to their important role in aminoacid synthesis as methyl transfer agents. The crystals of many betaine complexes display interesting physical properties, exhibiting phase transitions with ferroelectric, antiferroelctric and ferroelastic behavior. Betaines containing a hydrophobic chain in the range of 8–20 carbon atoms show the unique properties characteristic for amphoteric surfactants and their current industrial application is in toiletries and personal care products. The conformational structure of zwitterionic molecules depends on several factors. The electrostatic attraction between two charged groups depends strongly on arm flexibility (energy differences between rotational trans and gauche isomers), bulkiness and hydration of charged groups preventing their close approach, solvent and arm electrical properties which control electrostatic attraction between two opposite charged groups, and polarization of solvent around the molecule caused by the dielectric discontinuity between solvent and solute interior (image charge effect). Electrostatic interaction is the common determinant and probably the most important element in structure-reactivity correlation in organic and biological systems. On the other hand, organic compounds are thought to be pure even though they may be a mixture of conformational isomers. This is because the isomers covert rapidly with each other at room temperature and their individual reactivates are little known. Occasionally the conformers may be stabilized in the crystallographic matrixes of polymorphic structures. This article describes structures of seven groups of aliphatic, aromatic and alicyclic betaines and numbers of their new hydrogen-bonded complexes with mineral and organic acids.

20

Comparison of some properties and molecular structure of MHPOBC and chlorinated MHPOBC

75%

Bąk G. W.

Scientific Bulletin. Physics / Lodz University of Technology

|

2020

|

tom Vol. 41

5--21

EN

Comparison of molecular structure of MHPOBC and chlorinated MHPOBC has been made and presented in the paper. The main difference in molecular structure of MHPOBC and chlorinated MHPOBC molecules consists in different properties of two chemical bonds between the benzene ring with substituted chlorine atom and neighbouring parts of molecule. For chlorinated version of MHPOBC the component of molecular dipole moment perpendicular to the long axis of molecule is substantially smaller than for MHPOBC molecules. As a result of chlorination core of MHPOBC molecules becomes more flexible. These differences of molecular structure lead to easily noticeable differences in macroscopic properties of MHPOBC and its chlorinated version.

PL

Porównano strukturę molekuły i niektóre właściwości fizyczne MHPOBC i MHPOBC-Cl. Podstawowa różnica struktury molekuły polega na różnicy właściwości dwu wiązań chemicznych pomiędzy pierścieniem benzenowym zawierającym atom chloru a sąsiednimi fragmentami molekuły. Dla chlorowanej wersji MHPOBC obliczona składowa momentu dipolowego prostopadła do długiej osi molekuły jest istotnie mniejsza niż w przypadku molekuły MHPOBC. W wyniku zmiany właściwości niektórych wiązań molekuła MHPOBC-Cl staje się mniej sztywna. Konsekwencją tych różnic właściwości molekuł są istotne różnice właściwości fizycznych obydwu substancji.