Spektralna istraživanja spinelnog feritnog sistema NixZn1−xFe2O4

X-ray diffraction, DTA, IR and SEM investigations were carried out for a series of samples of the system NixZn1-xFe2O4 (with x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) prepared using the usual ceramic technique. The analysis of X-ray diffraction indicates that the samples have single phase with spinel cubic structure. The lattice constant (a), radius of tetrahedral ions (rtet), bulk density (D) and theoretical density (Dx) were found to decrease while the porosity (P) increases as the content of nickel ions (x) increases. SEM images indicate observable variations between the different compositions. IR absorption spectra showed the four characteristic peaks of ferrites. The position and intensity of the peaks are markedly composition dependent.Na nizu uzoraka sistema NixZn1−xFe2O4 (za x = 0,0, 0,2 , 0,4 , 0,6 , 0,8 i 1,0) pripremljenih uobičajenom keramičkom tehnikom, izvršena su mjerenja difrakcijom rendgenskog zračenja, diferencijalna termička analiza, optička mjerenja u infracrvenom području i snimanja skanirajućim elektronskim mikroskopom. Analiza difrakcije rendgenskog zračenja indicira da uzorci imaju jednu fazu sa spinelnom kubičnom strukturom. Nadeno je da konstanta rešetke, promjeri tetrahedralnih iona, volumna i teoretska gustoća padaju a poroznost raste s porastom sadržaja nikla. Slike dobivene skanirajućim elektronskim mikroskopom indiciraju primjetne promjene među različitim smjesama. Spektri infracrvene apsorpcije pokazuju četiri karakteristična vrha za ferite. Položaj i intenzitet vrhova značajno ovise o sastavu sistema

Spektralna istraživanja spinelnog feritnog sistema NixZn1−xFe2O4

X-ray diffraction, DTA, IR and SEM investigations were carried out for a series of samples of the system NixZn1-xFe2O4 (with x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) prepared using the usual ceramic technique. The analysis of X-ray diffraction indicates that the samples have single phase with spinel cubic structure. The lattice constant (a), radius of tetrahedral ions (rtet), bulk density (D) and theoretical density (Dx) were found to decrease while the porosity (P) increases as the content of nickel ions (x) increases. SEM images indicate observable variations between the different compositions. IR absorption spectra showed the four characteristic peaks of ferrites. The position and intensity of the peaks are markedly composition dependent.Na nizu uzoraka sistema NixZn1−xFe2O4 (za x = 0,0, 0,2 , 0,4 , 0,6 , 0,8 i 1,0) pripremljenih uobičajenom keramičkom tehnikom, izvršena su mjerenja difrakcijom rendgenskog zračenja, diferencijalna termička analiza, optička mjerenja u infracrvenom području i snimanja skanirajućim elektronskim mikroskopom. Analiza difrakcije rendgenskog zračenja indicira da uzorci imaju jednu fazu sa spinelnom kubičnom strukturom. Nadeno je da konstanta rešetke, promjeri tetrahedralnih iona, volumna i teoretska gustoća padaju a poroznost raste s porastom sadržaja nikla. Slike dobivene skanirajućim elektronskim mikroskopom indiciraju primjetne promjene među različitim smjesama. Spektri infracrvene apsorpcije pokazuju četiri karakteristična vrha za ferite. Položaj i intenzitet vrhova značajno ovise o sastavu sistema

Električna i termoelektrična svojstva čistog i supstituiranih bakrenih ferita

Samples of the CuFe2-xAlxO4 system with x=0, 0.2, 0.4 and 0.6 were prepared. The single phase spinel structure was verified by X-ray diffraction method. The thermoelectric power (a) and dc electrical resistivity (r) were studied as a function of temperature and composition. The results show that the resistivity increases and the transition temperature decreases with increasing the aluminium substitution. The activation energy in ferrimagnetic region is lower than that in paramagnetic region. The drift mobility of carriers increases exponentially with temperature as expected for ferrites.Priređeni su uzorci sistema CuFe2−xAlxO4 sa x = 0, 0,2, 0,4 i 0,6. Proučavana je termoelektrična sila i dc električna otpornost u ovisnosti o temperaturi i sastavu. Rezultati mjerenja pokazuju da se otpornost povećava a temperatura prijelaza smanjuje sa povećanjem koncentracije aluminija. Aktivacijska energija veća je u feromagnetskoj nego u paramagnetskoj fazi. U skladu s očekivanjem, ustanovljeno je da se mobilnost nosilaca naboja u feritima eksponencijalno povećava s temperaturom

Regioselective chlorination of phenols in the presence of tetrahydrothiopyran derivatives

Four six-membered cyclic sulfides, namely tetrahydrothiopyran, 3-methyltetrahydrothiopyran, 4-methyltetrahydrothiopyran and 4,4-dimethyltetrahyrdrothiopyran have been used as moderators in chlorination reactions of various phenols with sulfuryl chloride in the presence of aluminum or ferric chloride. On chlorination of phenol, ortho-cresol and meta-cresol the para/ortho chlorination ratios and yields of the para-chloro isomers are higher than when no cyclic sulfide is used for all of the cyclic sulfides, but chlorination of meta-xylenol is less consistent, with some cyclic sulfides producing higher p/o ratios and others producing lower ratios than reactions having no sulfide present

A tribute to Professor Keith Smith: commemorative issue in honor of Professor K. Smith on the occasion of his 65th anniversary

Keith received an MSc in 1969 and a PhD in 1971 for his work in this area and was awarded a Royal Society European Exchange Fellowship to take up a postdoctoral research position with Professor Albert Eschenmoser at the ETH in Zürich, Switzerland, where he contributed to a project on chlorophyll derivatives. While Keith was in Switzerland, Andrew Pelter moved to Swansea University to take up a position as Professor of Organic Chemistry and a lectureship became available there. Keith was appointed to the position from October 1972 and rejoined his ollaboration with Pelter on organoboron chemistry. Among other reactions, they introduced methods for syntheses of unsymmetrical conjugated diynes from the corresponding dialkyldialkynylborates, of secondary and tertiary alcohols from reactions of trialkylboranes with bis(phenylthio)alkyllithiums8 or 2-lithio-2- alkylbenzodithioles, of N-substituted sulfonamides, and of dialkylbromoboranes

Synthesis of new thiophene derivatives and their use as photostabilizers for rigid poly(vinyl chloride)

Five new thiophenes, namely, N-[(3-bromo-2-methylthiophen-5-yl)methylene]-4-methoxyaniline (4a), N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethoxyaniline (4b), N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethylaniline (4c), 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-methylquinazolin-4(3H)-one (4d), and 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-isopropylquinazolin-4(3H)-one (4e), have been synthesized. All of these materials brought about a reduction in the level of photodegradation of poly(vinyl chloride) (PVC) films containing the synthesized thiophenes (0.5%; by weight). The results obtained showed that the extent of photostabilization of PVC in the presence of an additive was in the order 4e > 4d > 4b > 4a > 4c. For the most favorable additive (4e), the rate of appearance of infrared absorption bands of degradation products was reduced by around two-thirds, while the quantum yield of chain scission was calculated to be reduced by a factor of more than one thousand. It is suggested that the additives may help stabilize PVC by direct absorption of UV radiation and dissipation of the energy as heat or that electrostatic attraction between the additives and PVC may assist transfer of energy from excited state PVC to the additive, from where it can be dissipated

Regioselective electrophilic aromatic substitution reactions over reusable zeolites

Zeolite catalysts can play an important role in the development of greener organic syntheses through their abilities to act as heterogeneous catalysts, support reagents, entrain by-products, avoid aqueous work-ups and enhance product selectivities via shape-selectivity. We have shown that zeolites under modest conditions can have advantages in para-regioselective nitration, alkylation, acylation, methanesulfonylation and halogenation of aromatic compounds. They can also assist in the electrophilic rearrangement of aryloxiranes. The zeolites can be easily removed from reaction mixtures by filtration and regenerated by heating and can then be reused several times to give the same selectivity

Crystal structure of 3-amino-2-ethylquinazolin-4(3H)-one

The mol­ecule of the title compound, C10H11N3O, is planar, including the ethyl group, as indicated by the N-C-C-C torsion angle of 1.5 (2)°. In the crystal, inversion-related mol­ecules are stacked along the a axis. Mol­ecules are oriented head-to-tail and display [pi]-[pi] inter­actions with a centroid-to-centroid distance of 3.6664 (8) Å. N-H...O hydrogen bonds between mol­ecules generate a `step' structure through formation of an R22(10) ring