The characterization of Rice Husk Ash (RHA) was carried out using conventional chemical analysis and instrumental techniques. Chemical analysis reveals that RHA contains mainly silica along with minor inorganic oxides. Phase analysis by X-ray diffraction (XRD) indicates the presence of quartz, crystobalite and anorthite, while micro structural features obtained from Scanning Electron Microscopy (SEM) shows that RHA particles are highly porous and honeycombed structure. Thermal analysis indicates the presence of surface moisture. A wide range of particles (0.001-0.100 mm) are present in the sample with 59% below the size of 0.05 mm. However after characterization, utilization of RHA as a potential cost effective ingredient in developing a variety of construction materials (e.g. building brick, insulating brick and pozzolana cement) have been examined. The results obtained are very promising.

Spiro compounds 7,11-diaryl-2,4-diazaspiro [5,5]undecane-1,3,5,9-tetraones 3a-d were prepared by carrying out reactions between diarylideneacetones, (ArCH=CH) 2 C=O, 2a-d [Ar= 2-CH 3 C 6 H 4 , 4-CH 3 C 6 H 4 , 4-(CH 3 ) 2 NC 6 H 4 and 4-HOC 6 H 4 respectively] and barbituric acid (1a) under refluxing condition in aqueous ethanol medium without using any catalyst. Under similar conditions the corresponding 7,11-diaryl-3-thioxo-2,4-diazaspiro [5,5]undecane-1,5,9-triones 3e-g were synthesized from the reactions of diarylideneacetones 2a, 2d and 2e [Ar= 4-ClC 6 H 4 ] with 2-thiobarbituric acid (1b). The structures of the spiro compounds were established with the help of their UV, IR, 1 H NMR, 13C NMR and mass spectral data and elemental analyses.

A number of 5, 7-diaryl-1,5-dihydro (or 1, 2, 3, 5-tetrahydro)-pyrano[2, 3-d] pyrimidin-2, 4-diones (or 2-thioxo-4-ones) (3a-f) have been synthesized in one-step by cyclocondensation of barbituric acid or thiobarbituric acid (1) with arylideneacetophenones (2a-c), in glacial acetic acid in the presence of phosphorous pentoxide. The structures of the compounds 3a-f have been determined by UV, IR, 1 H NMR, 13 C NMR, mass spectral data and elemental analyses.

Some new 5, 7-diaryl-1,5-dihydro (or 1, 2, 3, 5-tetrahydro)- pyrano[2, 3-d] pyrimidin-2, 4-diones (or 2-thioxo-4-ones) (3a-h) have been synthesized in one-step by cyclocondensation of barbituric acid or thiobarbituric acid (1) with arylideneacetophenones (2a-d), in glacial acetic acid in the presence of phosphorous pentoxide. The structures of the compounds 3a-h have been determined by UV, IR, 1H NMR, 13C NMR, mass spectral data and elemental analyses. The compounds 3a-h do not seem to be available in the literatureBangladesh J. Sci. Ind. Res. 51(2), 129-138, 2016

A simple and practical route for the Biginelli cyclocondensation reaction using anhydrous ZnCl2 as a catalyst in n-heptane-toluene medium by reaction of substituted benzaldehydes,1a-d (1a=2-ClC6H4-, 1b=2-BrC6H4- and 1c=4-ClC6H4-,1d=2-H3CC6H4-) with 1, 3-dicarbonyl compounds, 2a-b (2a= ethyl acetoacetate and 2b= acetylacetone) and urea or thiourea, 3a-b to give the corresponding Biginelli 3,4-dihydro- 1H-pyrimidin-2-ones and 1,2,3,4-tetrahydro pyrimidines, 4a-d. The structures of the compounds 4a-d were confirmed by their ultraviolet, infrared, 1H NMR, 13C NMR spectra and elemental analyses. Bangladesh J. Sci. Ind. Res.55(3), 173-180, 2020