Novel compounds of the general formula <FORM:1035097/C2/1> or the corresponding isomeric formula <FORM:1035097/C2/2> wherein R1 represents an alkyl radical containing 1 to 10 carbon atoms, a substituted alkyl radical containing 1 to 10 carbon atoms, an aryl radical containing 5 to 14 carbon atoms, a substituted aryl radical containing 6 to 14 carbon atoms, an aralkyl radical containing 5 to 15 carbon atoms, a substituted aralkyl radical containing 7 to 15 carbon atoms, an alkenyl radical containing 3 to 10 carbon atoms, an alkynyl radical containing 3 to 10 carbon atoms, a cycloalkyl radical containing 3 to 12 carbon atoms, a cycloalkenyl radical containing 4 to 12 carbon atoms, a substituted cycloalkyl radical in which the cycloalkyl radical contains 3 to 12 carbon atoms, a substituted cycloalkenyl radical in which the cycloalkenyl radical contains 4 to 12 carbon atoms, a cycloalkyl alkyl radical containing 4 to 13 carbon atoms, a cycloalkenyl alkyl radical containing 5 to 13 carbon atoms, a (substituted cycloalkyl) alkyl radical containing 5 to 14 carbon atoms or a cyano radical; R2 represents a hydrogen, chlorine, fluorine, bromine or iodine atom, a methyl radical, an ethyl radical, a propyl radical, a butyl radical, a methoxy radical, an ethoxy radical, a propoxy radical, a butoxy radical, a nitro radical, an alkoxymethyl radical containing 2 to 6 carbon atoms, a hydroxy alkyl radical containing 1 to 6 carbon atoms, an alkenyl radical containing 3 to 6 carbon atoms, a thiocyanato radical, a cyano radical, a mercaptomethyl radical, a methylthiomethyl radical, a phenylthiomethyl radical, an alkylthio radical containing 1 to 4 carbon atoms, a bromomethyl radical, a fluoromethyl radical, a chloromethyl radical or a carboxymethylthiomethyl radical; R3 represents a hydrogen, chlorine or bromine atom, an alkyl radical containing 1 to 5 carbon atoms, a chloroalkyl radical containing 1 to 4 carbon atoms, a bromoalkyl radical containing 1 to 4 carbon atoms, or an alkoxy radical containing 1 to 5 carbon atoms; or R2 and R3 together represent a divalent radical which forms, together with the carbon atoms to which R2 and R3 are attached, a 5-, 6- or 7-membered ring; R4 represents a covalent radical of molecular weight from 15 to 250 which is an alkyl radical containing 1 to 10 carbon atoms, a substituted alkyl radical containing 1 to 10 carbon atoms, a cycloalkyl radical containing 3 to 12 carbon atoms (which may be substituted), a cycloalkylalkyl radical containing 4 to 13 carbon atoms (which may be substituted), a phenyl radical, a substituted phenyl radical, a phenylalkyl radical, a substituted phenylalkyl radical, a dialkylamino radical containing 2 to 10 carbon atoms, an alkoxy radical containing 1 to 10 carbon atoms, a carbamyl radical, a substituted carbamyl radical, a thiocarbamyl radical, a substituted thiocarbamyl radical, a glycosyl radical, a cyano radical, an acyl radical, a carboxyethyl radical, a dialkoxyphosphoryl radical containing 2 to 6 carbon atoms, an alkylthio radical containing 1 to 12 carbon atoms, a bromoalkylthio radical containing 1 to 12 carbon atoms, a chloroalkylthio radical containing 1 to 12 carbon atoms, a benzylthio radical, a phenylthio radical, a halophenylthio radical, a mononitrophenylthio radical, a p-tert.-butyphenylthio radical, a dinitrophenylthio radical or a tolythio radical; and X represents an oxygen or sulphur atom, are prepared by methods known for related compounds, e.g. those disclosed in Specification 968,666. These compounds are herbicides (see Division A5). Compounds of the above formulae in which X is oxygen, R1 is as defined, R2 is halogen, R3 is methyl, and R4 is CCl3S- or RCO-, where R is hydrogen, C1- 4 alkyl, a mono- or polychloroalkyl radical of 1-4 C, phenyl, mono-, di- or trichlorophenyl, benzyl, mono-, di- or trichlorobenzyl, phenoxymethyl or mono-, di- or trichlorophenoxymethyl, are claimed as novel. b - Isopropylamino - N - isopropylcrotonamide is prepared from N-isopropylacetoacetamide and isopropylamine.ALSO:Compounds of the general formula <FORM:1035097/A5-A6/1> or the corresponding isomeric formula <FORM:1035097/A5-A6/2> wherein R1 represents an alkyl radical containing 1 to 10 carbon atoms, a substituted alkyl radical containing 1 to 10 carbon atoms, an aryl radical containing 5 to 14 carbon atoms, a substituted aryl radical containing 6 to 14 carbon atoms, an aralkyl radical containing 5 to 15 carbon atoms, a substituted aralkyl radical containing 7 to 15 carbon atoms, an alkenyl radical containing 3 to 10 carbon atoms, a cycloalkyl radical containing 3 to 12 carbon atoms, a cycloalkenyl radical containing 4 to 12 carbon atoms, a substituted cycloalkyl radical in which the cycloalkyl radical contains 3 to 12 carbon atoms, a substituted cycloalkenyl radical in which the cycloalkenyl radical contains 4 to 12 carbon atoms, a cycloalkyl alkyl radical containing 4 to 13 carbon atoms, a cycloalkenyl alkyl radical containing 5 to 13 carbon atoms, a (substituted cycloalkyl) alkyl radical containing 5 to 14 carbon atoms or a cyano radical; R2 represents a hydrogen, chlorine, fluorine, bromine or iodine atom, a methyl radical, an ethyl radical, a propyl radical, a butyl radical, a methoxy radical, an ethoxy radical, a propoxy radical, a butoxy radical, a nitro radical, an alkoxymethyl radical containing 2 to 6 carbon atoms, a hydroxy alkyl radical containing 1 to 6 carbon atoms, an alkenyl radical containing 3 to 6 carbon atoms, a thiocyanato radical, a cyano radical, a mercapto-methyl radical, a methylthiomethyl radical, a phenylthiomethyl radical, an alkylthio radical containing 1 to 4 carbon atoms, a bromomethyl radical, a fluoromethyl radical, a chloromethyl radical or a carboxymethylthiomethyl radical; R3 represents a hydrogen, chlorine or bromine atom, an alkyl radical containing 1 to 5 carbon atoms, a chloroalkyl radical containing 1 to 4 carbon atoms, a bromoalkyl radical containing 1 to 4 carbon atoms, or an alkoxy radical containing 1 to 5 carbon atoms; or R2 and R3 together represent a divalent radical which forms, together with the carbon atoms to which R2 and R3 are attached, a 5-, 6- or 7-membered ring; R4 represents a covalent radical of molecular weight from 15 to 250 which is an alkyl radical containing 1 to 10 carbon atoms, a substituted alkyl radical containing 1 to 10 carbon atoms, a cycloalkyl radical containing 3 to 12 carbon atoms (which may be substituted), a cycloalkylalkyl radical containing 4 to 13 carbon atoms (which may be substituted), a phenyl radical, a substituted phenyl radical, a phenylalkyl radical, a substituted phenylalkyl radical, a dialkylamino radical containing 2 to 10 carbon atoms, an alkoxy radical containing 1 to 10 carbon atoms, a carbamyl radical, a substituted carbamyl radical, a thiocarbamyl radical, a substituted thiocarbamyl radical, a glycosyl radical, a cyano radical, an acyl radical, a carboxyethyl radical, a dialkoxyphosphoryl radical containing 2 to 6 carbon atoms, an alkylthio radical containing 1 to 12 carbon atoms, a bromoalkylthio radical containing 1 to 12 carbon atoms, a benzylthio radical, a phenylthio radical, a halophenylthio radical, a mononitro-phenylthio radical, a p-tert-butylphenylthio radical, a dinitrophenylthio radical or a tolylthio radical; and X represents an oxygen or sulphur atom, are used to control the growth of weeds, e.g. in a composition containing additionally (i) a diluent which is at least in part an oil (defined as a liquid immiscible with water and soluble in ether, and boiling at not below 125 DEG C.), with or without a surface-active agent; (ii) a diluent which is at least in part a solid, with or without a surface-active agent; (iii) a surface-active agent and a diluent which is a liquid other than an oil, e.g. water; or (iv) a surface-active agent. The compositions may be in the form of solutions, dispersions, powders or dusts, granules or pellets, and may contain adhesives, corrosion inhibitors, antifoam agents, dyes, pigments, anticaking agents, hard water stabilizers and other herbicides, e.g. those of Specifications 1,035,091, 1,035,092, 1,035,093, 1,035,094, 1,035,095, 1,035,096 and 1,035,098 or substituted ureas, substituted trianzines, phenols, chloro-carboxylic acids and their derivatives, substituted carbamic acid derivatives, maleic hydrazide, inorganic salts, mixed inorganic-organic salts, or other specified herbicides.