The isomeric compounds nimbolide and isonimbolide

Nimbolide [systematic name: (4α,5α,6α,7α,15β,17α)‐7,15:21,23‐diepoxy‐6‐hydroxy‐4,8‐dimethyl‐1‐oxo‐18,24‐dinor‐11,12‐secochola‐2,13,20,22‐tetraene‐4,11‐dicarboxylic acid γ‐lactone methyl ester], C₂₇H₃₀O₇, was isolated from the leaves of Azadirachta indica, and its isomer, isonimbolide [systematic name: (4α,5α,6α,7α,15α)‐7,15:21,23‐diepoxy‐6‐hydroxy‐4,8‐dimethyl‐1‐oxo‐18,24‐dinor‐11,12‐secochola‐2,16,20,22‐tetra­ene‐4,11‐dicarboxylic acid γ‐lactone methyl ester], was prepared from a novel rearrangement reaction of nimbolide, using boron trifluoride etherate and tetra­butyl­ammonium bromide. The reaction conditions are probably responsible for the ether cleavage, double‐bond rearrangement and reformation of the ether linkage. As a result, there are conformational changes in two cyclo­pentane rings and the side‐chain –CH₂COOMe group. In isonimbolide, an (24) hydrogen‐bond motif is observed.     

Natural radioactivity and indoor radiation measurements in buildings and building materials in Gobichettipalayam town

Samples of natural and manufactured building materials used by the people of Gobichettipalayam town have been analyzed for ²²⁶Ra, ²³²Th and ⁴⁰K using gamma-ray spectrometry. Radium equivalent activity of the materials has been measured using the formula given by OECD and the geometric mean value of sand, clay and cements are found to be 53.53 Bq·kg⁻¹, 89.09 Bq·kg⁻¹ and 72.25 Bq·kg⁻¹, respectively. The radium equivalent activities obtained in the building materials are all well below the acceptable limit. The indoor gamma-dose has been measured using thermoluminescence dosimeters and it was found in the range of 1051.2–3946.0 μGy/year. The annual effective indoor gamma radiation dose to the people of Gobichettipalayam town has been found to be 0.8 mSv/y.     

Rotational disorder in 1,5-dihydroxy xanthone

The crystal structure of 1,5-dihydroxy xanthone obtained from Callophyllum trapezifolium has been determined (C₁₃H₈O₄), Mr = 228.21, a = 5.547(5), b = 5.186(5), c = 16.487(5) Å, = 91.40(1), Z = 2 and V = 474.1(6) ų. The xanthone molecule is planar and exhibits rotational disorder in the crystal. The packing of the molecules in the crystal lattice is due to inter- and intramolecular O–H O hydrogen bonds forming infinite chains.     

Background radiation study in Coimbatore city,Tamilnadu

The activity concentration and absorbed gamma dose rates due to primordial radionuclides (²³⁸U, ²³²Th and ⁴⁰K) have been determined for the soil of Coimbatore city using NaI(Tl) gamma-ray spectrometer. The average activity concentrations of ²³²Th, ²³⁸U and ⁴⁰K in the soil samples have been found to be 31.4 Bq·kg⁻¹, 12.8 Bq·kg⁻¹ and 698.0 Bq·kg⁻¹, respectively, which give the total gamma dose rate contribution of 56.4 nGy·h⁻¹. Grab sampling technique has been used to determine the indoor radon (²²²Rn) and thoron (²²⁰Rn) progeny levels in different dwellings in the city. The concentrations of radon and thoron progenies range from 0.4 to 10.4 and from 0.7 to 12.7 mWL with a mean value of 1.4 mWL and 3.1 mWL, respectively. The annual effective dose due to radon and thoron progeny has been found to be 0.14 mSv·y⁻¹.     

Thermoluminescence and photoluminescence studies on gamma irradiated CsI: Pb2+ crystals

Pure and Pb²⁺-doped CsI crystals have been grown by the Bridgemann technique. Optical absorption, thermoluminescence (TL) and photoluminescence (PL) measurements have been performed. In undoped and Pb²⁺-doped cesium iodide crystals, F-centers and V-centers have been produced at 770 nm and 350 nm, respectively. In Pb²⁺-doped crystals, additional centers at 373 nm, 290 nm and 258 nm bands have been produced. In undoped samples, only two glow peaks at 343 K and 373 K have been produced, and in Pb²⁺-doped samples additional glow peaks at 383 K and 423 K have been produced. For all the samples, TL emission, PL and excitation measurements have been performed.     

Natural radioactivity in the soil samples in and around Kudankulam nuclear power plant site

The terrestrial gamma-radiation in soil and sand samples collected around Kudankulam nuclear power plant site, i.e., in Radhapuram Taluk of Tirunelveli District has been measured using NaI(T1) gamma-ray spectrometer. In the soil samples total dose due to three primordial radionuclides lies in the range of 13.1–168.2 nGy/h with a geometric mean of 137.2 nGy/h, which yields an annual effective dose of 0.17 mSv/y. In the sand samples the total dose due to three primordial radionuclides has been found to be in the range of 38.1–1964.4 nGy/h with a geometric mean of 300.8 nGy/h, which gives an annual effective dose of 0.37 mSv/y which is well below the permissible limit (1 mSv).     

2′,3′‐Dehydrosalannol

The title compound, methyl (2aS,3R,5R,5aS,6S,6aS,8R,9aS,10aR,10bR,10cS)‐8‐(3‐furyl)‐2a,4,5,5a,6,6a,8,9,9a,10a,10b,10c‐dodeca­hydro‐3‐hydroxy‐2a,5a,6a,7‐tetra­methyl‐5‐(3‐methylbut‐2‐enoyl­oxy)‐2H,3H‐cyclo­penta­[4′,5′]­furo­[2′,3′:6,5]benzo[cd]­isobenzo­furan‐6‐acetate, C₃₂H₄₂O₈, was isolated from uncrushed green leaves of Azadirachta indica A. Juss (neem) and has been found to possess antifeedant activity against Spodptera litura. The conformations of the functional groups are similar to those of 3‐des­acetyl­salannin, which was isolated from neem kernels. The mol­ecules are linked into chains by intermolecular O—H?O hydrogen bonds.     

Structure of mangostin

The crystal structure of 1,3,6-trihydroxy-2,8-bis (3-methyl-2-butenyl)-9H-xanthen-9-one, Mangostin (C₂₄H₂₆O₆) isolated from the fruit hulls of Garcinia mangostana, Guttiferae is reported. The compound crystallizes in space group , with cell parametersa = 11.194(5), b = 13.450(5), c = 9.875(5) Å, = 108.13(5), = 108.13(5), = 99.64(5)°. The mean planes of the two isoprenyl side chains are oriented at an angle 49.6° in this structure while it is 159.8(2)° in mangostin acetate. The packing of the molecules is due to the solvent mediated network of hydrogen bonds. The conformation and packing of molecules are also different from mangostin acetate.     

Studies of linear correlation factor of dielectric polarization and excess dipolar free energies of amides in apolar solvents

The Kirkwood-Frohlich correlation factor (g), Eyring’s parametersG and G^* and the dipolar excess free energies of dilute solutions of formamide, acetamide,N-methyl acetamide,N,N-dimethyl formamide andN,N-dimethyl acetamide in 1,4-dioxan/benzene were obtained from a measurement of their static dielectric permittivities at 308 K. The fluid structure of these amides is discussed. Both in formamide and acetamide a dimeric linear chain with the individual dipoles more or less parallely oriented is preferred. InN-methyl acetamide, the antiparallel orientation of dipoles at lower concentrations turns into a parallel orientation with increase of concentration. In tertiary amides, with increase of concentration, parallel orientation of dipoles with global value ofg tending to unity is observed. The dipolar excess free energy of mixing in a given solvent is of the order primary amide > secondary amide > tertiary amide.