Organic Chemistry

An environmentally benign and one-pot method for the synthesis of 1-naphthol azo dyes has been developed by using polymer-supported periodic acid (PPIA) as a new solid acid via grinding followed by a diazo coupling reaction by 1-naphthol under solvent-free conditions at room temperature. The obtained aryl diazonium salts supported on polymer (aryl diazonium polymer periodate), ArN2 +IO4 - were sufficiently stable to be kept at room temperature in the dry state. This method has the advantages such as: eco-friendly, heterogeneous reaction conditions, simple experimental procedure, high purity. The structures of the products have been characterized by several techniques using UV-Vis, FT-IR, 1H NMR, 13C NMR and mass spectra.

Volatile oils of Dioclea reflexa (Fabaceae) roots were obtained by hydrostillation and analysed using GC and GC-MS. A total of 15 compounds were identified; hydrocarbons being the dominating group of the compounds representing 69.27 %. Oxygenated monoterpenoids identified included terpinen-4-ol (2.47 %), myrtenal (1.69 %), verbenone (1.25 %), trans-pinocarveol (2.86 %) and thymol (1.30 %); also stearyl iodide (10.33 %) was identified.

Characterization of the ethanolic extract of Randiaaccuminata stem (chewing stick) was carried out using Fourier Transform Infrared (FTIR) Spectrophotometer. The result of the analysis showed that the stem of Randiaaccuminata contain primary and secondary amines, aliphatic amine, alkyl halide, aromatic amine, nitro compounds, alkyne, alkanes, chloride and fluoride ions. The chloride and fluoride ions present in this plant is responsible for its cleaning property. It also prevents tooth decay, remove tooth stain, eliminates tooth aches and also promote cleaner teeth.

Thin layer chromatographic technique with silica gel – ethyl acetate adsorbent - solvent system has been validated for the determination of herbicides. Precision of the method determined in terms of reproducibility yielded relative standard deviation of 0.3 % and 0.5 % for the Rf of the herbicides and diameter of spots respectively. The minimum detectable quantity (MDQ) of the herbicides ranges from 0.20 – 0.50 ng. The method has been applied to determine the efficiencies of acetone, acetonitrile, methanol, hexane and acetone/hexane (4:1) for the recovery of the herbicides, atrazine, ametryne, propanil, diuron and nitrofen in a forest zone soil in Ghana. Acetone and acetonitrile were found to have approximately equal efficiency as extraction solvents. Extraction with acetone, acetonitrile, acetone/hexane (4:1) yielded more than 90% recovery for all the herbicides. The highest recovery efficiency of 96.2% was obtained for atrazine using acetone. Extraction with methanol and hexane gave relatively low recoveries particularly, with the clean up extracts. In all, the clean up procedure with SPE cartridge equipped with C-18 as adsorbent reduced recovery by 9 – 13 %.

A novel series of 2-substitutedimino-6-amino-4-[2-isobutoxy-5(4-methyl-5-carboxy-1,3-thiazo-2-yl)]-phenyl-1,3,5-thiadiazines had been recently synthesized in this laboratory by refluxing 2-(3-substitutedthioamidoforma midino-4-isobutoxyphenyl)-4-methyl-5-carboxy-1,3-thiazoles with various isocyanodichlorides in acetone-ethanol medium in 1:1 molar proportion for 2 hours. The structures of all the synthesized compounds were justified on the basis of chemical characteristics, elemental analysis and spectral studies.

Condensation of ethyl acetoacetate 2 with thiosemicarbazide 1a gave hydrazone derivative 4 not pyrazolone 5. Pyrazolone 5 can be obtained by treatment of 4 with 5 % sodium hydroxide in ethanol. Reactions of 4 with phencyl bromide, aryl diazonium chloride , arylidene malononitrile afforded pyrazole derivatives 6, 7 and pyranopyrazole 8 respectively. Also, treatment of 4 with dimethylformamide dimethyl acetal (DMFDMA) gave compound 11 not 9 nor 10. Reactions of pyrazole derivatives 6 with arylidene malononitrile afforded condensed compound 15 which was obtained by reaction with aromatic aldehydes. While reaction of 6 with DMFDMA gave the corresponding enamine 16.

In an attempt to control multidrug resistant bacteria, a library of some new heterocyclic derivatives containing pyrazoline, isoxazole and pyrimidine ring systems bearing 1,3,5- triazine core were designed and synthesised from chalcones. Chalcones (AI-AV) react with hydrazine hydrate / glacial aceticacid, hydroxylamine hydrochloride / alkali and guanidine hydrochloride / alkali gives 1-acetyl pyrazoline (BI-BV), isoxazole (CI-CV) and 2-amino pyrimidine (DI-DV) derivatives respectively. The structures of all the newly synthesised compounds were assigned on the basis of FTIR, 1H NMR, 13C NMR spectral data as well as elemental analysis. In vitro antimicrobial proficiency of the title compounds were assessed against selected pathogens. The minimum inhibitory concentration (MIC) was determined by broth dilution method and recorded at the lowest concentration inhibiting growth of the organism. Compounds BI, BII, CII, CIII and DV exhibited excellent antimicrobial activity and said to be the most proficient members of the series.

The leaves of Sida acuta “Broom Weed” (Family: Malvaceae) was analysed for its proximate, anti-nutrients and mineral elements composition using standard methods. The proximate analysis showed the results to be (%) moisture 54.82, ash 7.94, crude protein 17.85, crude fat 2.70, carbohydrate 6.21, crude fibre 5.30, and caloric value 360.54 Kcal. The concentration of anti-nutrients (mg/100g) was observed to be oxalate 140.8, hydrocyanic acid 98.3, phytate 210.1 and tannin 603.7. The mineral element contents (mg/100g dry weight) were Na (81.90), K (117.40), Ca (44.32), P (1.15), Fe (1.01), Zn (1.07) and Mg (14.40). The study showed that the high concentration of anti-nutrients in Sida acuta Burn.f. obtained from this locality might cause health hazard if consumed in large quantity over a long period of time.

Ce(IV) ion and sulphate ion loaded MCM-41 materials effectively catalyze the condensation of 1,2-aromatic diamine with 1,2-diketones to afford quinoxaline derivatives under milder reaction conditions. Significant role of concentration of Ce(IV) ion has been investigated and comparative studies of catalytic efficiencies of both Ce-MCM-41 and sulfated MCM-41 have also been discussed.  Both reagents are found to efficient and reusable with consistent catalytic activity.