1-(2-Mercaptoethyl)phthalazines and related compounds

1-(2-Mercaptoethyl)phthalazine (VII) and its analogs such as S-2-(1-phthalazyl)ethyliso-thiuronium bromide (VI), sodium S-2-(1-phthalazyl)ethylthiosulfate (VIII), 1,3-bis-acetylthio-2-(1-phthalazyl)propane (XII), 2-(1-phthalazyl)-1,3-propanedithiol (XIII), disodium 2-(1-phthalazyl)-1,3-propanedithiosulfate (XIV), 3-dimethylamino-2-(1-phthalazyl)-1-propanethiol (XVII) and 3-(4-methyl-1-piperazinyl)-2-(1-phthalazyl)-1-propanethiol (XIX) have been prepared as potential radiation protection agents.     

The synthesis of pyrimido[4,5-c]pyridazines and pyrimido[5,4-c]pyridazines

The Hofmann reaction on 6-methylpyridazine-3,4-dicarboxamide (1) gave a mixture of 3-methylpyrimido[4,5-c]pyridazine-5,7-dione (2), 3-methylpyrimido[5,4-c]pyridazine-6,8-dione (3) and an acid (4) of unknown structure. The Hofmann reaction on pyridazine-3,4-dicarboxamide (9) gave a mixture of pyrimido[4,5-c]pyridazine-5,7-dione ( 10 ) and an acid ( 11 ) of unknown structure. The reaction of 3-amino-6-methylpyridazine-4-carboxamide ( 18 ) with ethyl orthoformate gave 3-methylpyrimido[4,5-c]pyridazin-5-one ( 21 ). 4-Aminopyridazine-3-carboxamide ( 36 ) upon fusion with urea gave pyrimido[5,4-c]pyridazine-6,8-dione ( 37 ) while with ethyl orthoformate 36 gave pyrimido[5,4-c]pyridazin-8-one ( 38 ). Pyrimido[5,4-c]-pyridazine-8-thione ( 39 ) was obtained by the action of phosphorus pentasulfide on 38. 4-Amino-3-cyanopyridazine ( 16 ) when treated with formamide produced 8-aminopyrimido[5,4-c]-pyridazine ( 41 ). The synthesis of 4-aminopyridazine-3-carboxamide ( 36 ) and 4-amino-3-cyanopyridazine ( 16 ), both key intermediates in the synthesis of the novel pyrimido[5,4-c]pyridazine ring system was accomplished by the Reissert reaction of 4-aminopyridazine-2-oxides and subsequent conversion of the nitrile to the amide.     

100-150 MW designs of two- and three-cavity gyroklystron amplifiersoperating at the fundamental and second harmonics in X- andKu-bands

Efficient 100-150 MW X- and Ku-band microwave sources with pulselengths of 1 μs are being developed for driving future linear colliders. Two- and three-cavity co-axial designs of relativistic gyroklystron amplifiers are presented here which fulfill these requirements. Numerical simulations predict over 40% efficiency, 45-50 dB gain, and 100-160 MW power level for the gyroklystron designs operating at fundamental (8.568 GHz) and second harmonic (17.136 GHz). It is shown that introducing a penultimate (buncher) cavity significantly improves efficiency and gain of the second-harmonic amplifier     

Local fields near the surface of a crystalline dielectric

We calculate the variation of the local electric field with depth near the surface of a crystalline dielectric, for the cases of induced atomic dipoles oriented perpendicular and parallel to the surface. The crystalline dielectric is modelled by a cubic lattice of polarizable atoms, with the surface in the (001) plane. Our calculations show that the departure of the local field from its bulk value is confined almost entirely to the outermost plane, and even there is small (at the most a few percent).     

The synthesis of 1,2,5-thiadiazolo[3,4-d] pyridazines

A number of previously unreported 1,2,5-thiadiazolo[3,4-d]pyridazines in this relatively unexplored ring system have been reported, charaeterized and screened for antibacterial and antifungal activity.     

The crystal structure of 5-amino-6-chloro-4-nitro-2-(β-D-ribofuranosyl)-2H-pyridazin-3-one

The nucleoside, 5-amino-6-chloro-4-nitro-2-β-D-ribofuranosyl-2H-pyridazin-3-one ( 4 ), was synthesized as part of a study to prepare potential chemotherapeutic compounds. An X-ray crystal structure study of the compound was initiated in order to substantiate its formula and to examine its conformation and absolute configuration. The structure was determined using direct methods and refined to an R of 0.020 (R_w = 0.024). The compound has a glycosyl torsion angle of 71.2°. The structure contains three intermolecular hydrogen bonds and one intramolecular hydrogen bond.     

Polarizable biphenyl polysiloxane stationary phase for capillary column gas chromatography

A crosslinkable biphenylmethylpolysiloxane stationary phase was synthesized for capillary column gas chromatography and compared with methyl, phenyl, and cyanopropyl polysiloxane stationary phases for the separation of isomeric polycyclic aromatic compounds. While the new phase gave similar separations of nonpolar isomers when compared to the nonpolar phases, separations of polar isomers were greatly improved because of the induced polarity of the biphenyl group of the stationary phase by the solute molecules. This polarizable stationary phase offers a unique selectivity which is not available in other stationary phases.     

Nonextractable cyanopropyl polysiloxane stationary phases for capillary chromatography

Summary Crosslinkable cyanopropylpolysiloxane stationary phases have been difficult to produce because of steric effects of the large cyanopropyl groups or because of the interaction between the polar cyanopropyl groups and the groups added for crosslinking. Various polymers containing 50% to 90% cyanopropyl were synthesized which contained vinyl,p-tolyl, or 4-vinylphenyl groups for crosslinking. Thep-tolyl group was found to give satisfactory crosslinking if there were two such groups attached to one silicon atom.