1.2 Classification of surface-active substances
All surface-active substances can be divided into two large groups: ionogenic compounds, dissociating on ions at dissolution in water, and non-ionogenic (nonionic) compounds, which do not dissociate on ions.
Depending on a type of ions, which cause superficial activity of ionogenic substances – anions or cations – ionogenic substances are subdivided on anion-active, cation-active and ampholytic. Ampholytic SAS contain one or several functional groups and can act as anionic or cationic surface-active substance depending on pH of its water solution. Ampholytic compounds in acid solutions have cation-active properties, and in alkaline solutions – anion-active properties. Solubility of non-ionogenic substances in water is caused by functional groups having strong affinity to water.
A general feature for substances of both the groups is the fact that they are distributed on an interface of phases and change superficial properties of a system in whole. A scheme, illustrating the classification of surface-active compounds, including synthetic detergents, is represented on fig.1.1. Detailed SAS classification, approved by the V International congress on surface-active substances (Barcelona, 1968), is given in the table 1.
Among surface-active substances produced at the present time and applied as synthetic detergents, anion-active substances have the greatest distribution; anion-active substances output achieves 68 % from the total manufacture of synthetic detergents. Manufacture of non-ionogenic detergents makes only 29 % from the total volume, however now this value appreciably grows. Cation-active substances practically do not have washing properties and they are basically applied as extremely strong bactericidal additives or in a mixture with anionic or non-iogenic substances. Their manufacture makes 5 % from the total manufacture of SAS.
Fig.1.1. Classification of surface-active substances
Table 1. Classification of SAS according to active ion
A type of a compound |
A representative |
A chemical formula |
Anion-active surface-active substances |
||
Soaps |
Sodium stearate |
CH3(CH2)16COO-Na+ |
Sulphated spirits |
Sodium laurilsulphate |
CH3(CH2)l0CH2OSO3-Na+ |
Sulphated ethers |
|
R (OCH2CH2)nOSO3-Na+ |
Sulphated carboxylic acids |
Na-salt of sulphated oleic acid |
CH3 (CH2)7CH (CH2)8COO-Na+ OSO3-Na+ |
a-olefine sulphonates |
|
RCH=CHSO2ONa |
Petroleum sulphonates |
|
Contain SO3- and Na+ |
Sulphated aromatic hydrocarbons |
Linear alkyl sodium benzene sulphonates |
CH3CH (CH2)nCH3 SO3-Na+ |
Sulphated ethers |
Na-laurilsulphacetate |
CH3(CH2)l0CH2OCOCH2SO3-Na+ |
Sulphated amides |
|
R CH3 |
Sulphated oxyethylated alkyl phenols |
|
RC6H4O (CH2CH2O)nCH2CH2SO3-Na+ |
Acyl amino acids |
|
C H3(CH2)9CH2CONCH2COOH CH3 |
Metal alkyl phosphates |
Sodium polyphosphate |
Na5 R5 (P3O10)2R=C8H17 |
Cation-active surface-active substances |
||
Quaternary ammonium salts |
Initial amines Secondary amines Tertiary amines |
RN+ (CH3)3Cl - R2N+ (CH3)2Cl- R3N+ (CH3)Cl- |
Acetylated polyamines |
|
RCONH (CH2)3 N+ (CH3)3CH3COO- |
Salts of benzyl ammonium |
|
CH2N+ (CH3)2RCl-
C6H5 |
Non-ionogenic surface-active substances |
||
Ethers of multinuclear spirits and high acids |
Monoglycerine stearate |
CH2OHCHOHCH2OOC(CH2)I6CH3 |
Oxyethylated amines |
|
(CH2CH2O)уH
|
CONCH2CH2S3-
Na+
(CH2CH2O)XH
x+y = 5 RCH2N
|
|
|
|
Oxyethylated high fat acids |
Polyethylene glycol monostearate |
CH3(CH2)15CH2COO(CH2CH2O)nCH2 CH2OH |
|
Ethers of polyalkylene glycols and alkyl phenols |
Polyoxyethylene alkyl phenol |
O (CH2CH2O)6CH2CH2OH
C6H5 R = C8–C12
R
|
|
Products of condensation of fat acids and alkanol amines |
Diethanol amine stearate |
CH2CH2OH CH3(CH2)15CH2CON
CH2CH2OH |
|
Tertiary acetylene glycols |
4,7-dimethyl-5-decin-4,7-diol |
CH3 CH3 CH3CH2CH2CC=CCCH2CH2CH3
OH OH |
|
Polyoxyethylated alkyl phosphates |
|
C8HI7OP(O) [(OCHCH2)nOCH2CH2OH]2 |
|
Ampholytic surface-active substances |
|||
Betains |
|
R CHCOO-Na+
N+(CH3)3Cl- |
|
Amino acids |
|
R CHCOO-Na+
N+H3Cl- |
|
