The invention comprises N-substituted alkane sultams of the general formula <FORM:0810356/IV (b)/1> wherein R represents an aryl, hetero-aryl, aralkyl or hetero-aralkyl group which may be substituted by halogen or by alkyl, amino, nitro, acylamino, alkoxy or hydroxy groups, or by a group of the formula <FORM:0810356/IV (b)/2> and n represents 3 or 4, and the preparation thereof by reacting the required substituted or unsubstituted amine containing one or two primary amino groups with the required g - or d -halogeno-alkane sulphohalide, preferably in the presence of an acid-binding agent, to form an N-substituted halogeno alkane sulphonamide of the formula Hal-(CH2)nSO2NHR where n and R have the above significance and Hal represents a halogen, and heating the sulphonamide with or without an alkali metal hydroxide or other acid binding agent. The above process may be modified in that the corresponding g - or d -hydroxy-alkane-sulphonamide or ester thereof such as an ester derived from a carboxylic acid, e.g. acetic or benzoic acid, or from a sulphonic acid such as methane or p-toluene sulphonic acid may be used to form the corresponding sulphonamide, water, or the corresponding carboxylic or sulphonic acid respectively being split off during the ring closure step to form the desired sultam, or the corresponding ether may be used to form an N-substituted-alkane-sulphonamide of the formula R1O(CH2)nSO2NHR, wherein R and n have the above significance and R1O is an ether group, an ether or phenol being split off during the ring closure step by heating. The above process may also be modified in that the required primary amine of the type referred to above is reacted with the required halogenoalkane substituted in the g - or d -position with a sulphonic acid radical or ester thereof or a radical which may be subsequently converted into a sulphonic acid group, e.g. a mercapto, disulphide or rhodane group which may be converted into a sulphonic acid group by oxidation, or a halogen atom or sulphonyloxy group which may be converted into a sulphonic acid group by reaction with an alkali metal sulphite to form an amino-substituted alkane sulphonic acid which is then treated to effect ring closure, e.g. by the action of phosphorus oxychloride or phosphorus trichloride. This process may also be modified in that sulphonic acid esters of the corresponding hydroxy alkane sulphonic acids are used for the production of the amino-substituted alkane sulphonic acid. New substituents may be introduced into the R group of the N-substituted alkane sultams or into the R group of the amine or sulphonamide intermediate compounds, e.g. by nitrating or halogenating. Substituents already present in the R group may be modified, e.g. an acylamino group may be deacetylated, an alkoxy group may be saponified or a nitro group may be reduced. In the examples: (a) 4-chloro butane sulphochloride is reacted with each of the following amines to form the corresponding 4-chloro butane sulphonamides which are then cyclized to the corresponding sultams: aniline, o-, m- and p-toluidine, m-, and p-nitraniline, o- and p-anisidine, a - and b -naphthylamine, p-aminoacetanilide, 2- and 3-aminopyridine, p-(b - diethylaminoethoxy) - aniline, 4 - methoxy-3-nitro-aniline, 5-, 6- and 8-aminoquinoline, 6-amino - isoquinoline, 8 - aminomethoxy - quinoline, 5 - amino - 8 - acetamino - quinoline, b -phenylethylamine, b - pyridylmethylamine, and p-nitrobenzylamine; (b) 3-chloro propane sulphochloride is reacted with aniline and with p-aminoacetanilide to form the corresponding 3-chloro propane sulphonamides which are then cyclized to the corresponding sultams; (c) the sodium salt of 4-chloro-butane sulphonic acid is reacted with aniline and with p-chloroaniline to form the corresponding 4-arylaminobutane sulphonic acids which are then cyclized to the corresponding sultams; (d) butane sultone (1,4) is reacted with o-toluidine to form 4-(o-toluidino)-butane sulphonic acid which is then cyclized to form the sultam of 4-(o-toluidino) butane sulphonic acid; (e) N-phenyl butane sultam (1,4) is prepared by treating 4-phenoxy-butane sulphonic acid anilide with sodium hydroxide; (f) 4-acetoxy-n-butane-1-sulphonic acid chloride is reacted with p-anisidine and with aniline to form the corresponding sulphonamides which are then cyclized to the corresponding sultams, and 4-benzoyloxy - n - butane - 1 - sulphonic acid chloride is reacted with p-anisidine to form the corresponding sulphonamide which is then cyclized to the corresponding sultam; (g) 4-acetoxy-n-butane-1-sulphonic acid p-anisidide and anilide are refluxed with hydrochloric acid to form 4-hydroxy - n - butane - 1 - sulphonic acid p anisidide and anilide respectively which are then cyclized to form the sultams of 4-(p-anisidinc)-and 4 - anilino - n - butane - 1 - sulphonic acids; (h) the sultams of 4-(p-amino-phenylamino)-butane sulphonic acid and of 3-(p-aminophenylamino) - propane sulphonic acid are of 3 - (p - aminophenylamino) - propane sulphonic acid are prepared by hydrolysing the corresponding p-acetaminophenylamino compounds; (i) the sultams of 4-(4- and p-aminophenylamino)-butane sulphonic acids are prepared by reducing the corresponding m- and p-nitrophenyl with sodium sulphide, and the sultams of 4-(o-, m- and p-aminophenylamino)-, 4 - (2,4 - diaminoanilino) -, 4 - (41 - methoxy - 31 - aminophenyl) -, and 4 - (p - aminobenzyl)-butane sulphonic acids are prepared by reducing the corresponding nitrophenyl and nitrobenzyl compounds with hydrogen in the presence of Raney nickel; (j) the sultams of 4 - (2,4 - dinitranilino) - and 4 - (2,4 - dinitro-p-toluidino)-sulphonic acids are prepared by nitrating with nitric acid the corresponding anilino and toluidino compounds; (k) the sultam of 4-(p-hydroxy-anilino)-butane sulphonic acid is prepared by treating the corresponding p-amino-anilino compound with concentrated sulphuric acid; and (l) 4-chlorobutane sulphochloride is reacted with p-phenylene diamine and with benzidine to form N,N1 - di - (41 - chloro - butane - sulphonyl) - p-phenylene diamine and benzidine respectively which are then cyclized to the corresponding disultams of p-phenylene-bis-(4-amino-butane sulphonic acid) and of 4,41-diphenyl-bis-(4-amino-butane sulphonic acid). Specification 786,059 is referred to.ALSO:The invention comprises N-substituted alkane sultams of the general formula <FORM:0810356/IV (c)/1> wherein R represents an aryl, hetero-aryl, aralkyl or hetero-aralkyl group containing an azo substituent, and n represents 3 or 4, and the preparation thereof by diazotizing the corresponding sultams in which R represents an aryl, hetero-aryl, aralkyl or hetero-aralkyl group containing an amino substituent. In an example 4-(m- and p-aminophenyl) N-butane sultams are diazotized and coupled with b -naphthol. 4-(2,4 - Diaminophenyl) N - butane sultam may also be tetrazotized and coupled with phenols.