Peter Brownsort

Biochar, Tool for Climate Change Mitigation and Soil Management

Biochar is the solid remains of any organic material that has been heated to at least 350oC in a zero-oxygen or oxygen-limited environment, which is intended to be mixed with soils. If the solid remains are not suitable for addition to soils, or will be burned as a fuel or used as an aggregate in construction, it is defined as char not biochar. There is a very wide range of potential biochar feedstocks, e.g., wood waste, timber, agricultural residues and wastes (straws, bagasse, manure, husks, shells, fibers, etc.), leaves, food wastes, paper and sewage sludge, green waste, distiller’s grain, and many others. Pyrolysis is usually the technology of choice for producing biochar, though biomass gasification also produces smaller char yields. Syngas and pyrolytic bio-liquids, which have a potential use as energy carriers, are produced alongside biochar.

Intramolecular cycloaddition reactions involving nitrile sulphides

ortho-(Phenylpropioloxy)benzonitrile sulphide, generated in situ by thermal decarboxylation of the oxathiazolone (1), undergoes intramolecular 1,3-dipolar cycloaddition forming the chromenoisothiazole (4a); ortho-cinnamoylbenzonitrile sulphides also yield (4), together with nitrile, chromenoquinoline and amino-chromene by-products.

Nitrile sulphides. Part 7. Synthesis of [1]benzopyrano[4,3-c]isothiazoles and isothiazolo[4,3-c]quinolines

O-Hydroxybenzonitrile sulphide (1a), generated by thermal decarboxylation of the corresponding 1,3,4-oxathiazol-2-one, reacts with dimethyl acetylenedicarboxylate to afford methyl 4-oxo-4H-[1]benzopyrano[4,3-c]isothiazole-3-carboxylate (6a), from which the parent ring system (6c) can be prepared by hydrolysis and decarboxylation. The same products are formed from the acetoxy analogue (1b)via hydrolysis of isothiazole (5b). O-Acetamidobenzonitrile sulphide (1c) reacts similarly forming isothiazole (5c) and subsequently isothiazolo[4,3-c]quinolin-4(5H)-one (7c) by hydrolysis, ring closure, and decarboxylation. Cycloadditions to ethyl cyanoformate, ethyl propiolate, and diethyl fumarate have also been examined.

Nitrite sulphides. Part 10. Intramolecular 1,3-dipolar cycloadditions

Intramolecular 1,3-dipolar cycloadditions involving acetylenic and olefinic esters of o-hydroxybenzonitrile sulphide have been examined. The nitrite sulphides were generated by thermal decarboxylation of the corresponding 1,3,4-oxathiazol-2-one. o-Phenylpropiolyloxy and -amido derivatives (1a) and (2a) afforded chromeno[4,3-c]isothiazolone (7a)(70%) and isothiazolo[4,3-c]quinolinone (9a)(81%) respectively. Four products were formed on thermolysis of cinnamate esters (10); o-cyanophenyl cinnamates resulting from desulphuration of the nitrite sulphide; chromenoisothiazolones (7) from Intramolecular cycloaddition followed by dehydrogenation of the resulting 4,5-dihydroisothiazole; chromeno[4,3-b]quinolinones (14); and 4-amino-3-benzylchromenones (15). The last two compounds are believed to be formed by a pathway involving the 2,5-dihydroisothiazole tautomer (17), extrusion ofsulphur, followed by cyclisation or hydrogenation (Scheme 2). α- and β-Methylcinnamate esters (19) and (20) afforded, in addition to nitrite by-products, dihydroisothiazole (21) and 4-amino-3(α-styryl)chromenone (23) respectively.