Patent GB-769718-A (GB)
Title: Substituted phthalidyl phenols
IPC: C07D307/88
Filed: 1954-10-18
Abstract: Phthalidyl phenols substituted in the phenolic ring by at least one hydrocarbon substituent which contains more than one carbon atom, are used as antioxidants for synthetic rubbers such as polychloroprene, butyl rubber, copolymers of butadiene and styrene, copolymers of butadiene and acrylonitrile.  The preferred antioxidants have the formula <FORM:0769718/IV(a)/1> wherein R is an aromatic radical having 1 to 4 substituents thereon, said substituents being selected from alkyl groups wherein at least one alkyl group has more than one carbon atom, phenyl groups, phenyl alkyl groups and cycloalkyl groups, and preferably at least one substituent containing a secondary or tertiary carbon atom.  The phenolic radical may be mono, di or polyhydroxy or may be a naphthol radical.  Examples of the antioxidants include 2(3 - phthalidyl)6 - t - butyl - p - cresol, 4(3-phthalidyl)6 - t - butyl - o - cresol, 3 - phthalidyl - mono - t - butyl - o - isopropyl phenol, phthalidyl - mono - phenylethyl - p - cresols, o-phthalidyl - mono - octyl - p - cresols, phthalidyl-p - t - butyl - o - cresol, phthalidyl - p - isooctyl phenols, and phthalidyl-2,4-di-t-butyl phenols.ALSO:The invention comprises phthalidyl phenols substituted in the phenolic ring by at least one hydrocarbon substituent which contains more than one carbon atom. The preferred compounds have the formula <FORM:0769718/IV(b)/1> wherein R is an aromatic radical having from 1 to 4 substituents thereon, said substituents being selected from alkyl groups wherein at least one alkyl group has more than one carbon atom, phenyl groups, phenylalkyl groups and cycloalkyl groups.  The aromatic radical may be a single or double benzene ring. Preferably R represents a benzene ring containing a secondary or tertiary alkyl group ortho or parato the hydroxyl group. Generally at least one alkyl substituent contains from 2 to 10 carbon atoms.  The phenol may be mono-, di- or polyhydroxy, and may contain ring-substituents in any position not occupied by a hydroxyl group.  The novel products may be prepared by condensing o-phthalaldehydic acid with an approppriate substituted phenol, in the presence of a condensing agent, such as sulphuric acid, chlorosulphonic acid, phosphorous pentoxide, boron trifluoride and aluminium chloride.  The temperature is not critical and may vary over a considerable range although it is preferably kept below room temperature.  The products are useful as non-staining antioxidants for natural and synthetic rubbers and may be used in crude form or may be purified by washing with water and drying. In examples, o-phthal-aldehydic acid is reacted in the presence of sulphuric acid with (1) mono-t.-butyl-o-iso-propyl phenol; (2) p-t.-butyl-o-cresol; (3) o-t.-butyl - o - cresol; (4) mono - o - a  - phenylethyl-p-cresol; (5) mono-octyl-p-cresol, and o-t.-butyl-p-cresol.  Representative of the products are phthalidyl - mono - t. - butyl - o - isopropyl phenols, phthalidyl - p - t - butyl - o - cresol, 4 - [3 - phthalidyl] - 6 - t. - butyl - o - cresol, phthalidyl - mono - a  - phenylethyl - p - cresols, phthalidyl - mono - octyl - p - cresols, and 2 - [3-phthalidyl]-6-t.-butyl-p-cresol.ALSO:Phthalidyl phenols substituted in the phenolic ring by at least one hydrocarbon substituent which contains more than one carbon atom, are used as antioxidants for natural rubber, chlorinated rubbers and rubber hydrochloride, and as age resistors for raw rubber in latex form, coagulated rubber latices or vulcanized rubbers, in amounts of from 0,25 to 5 per cent by weight, preferably 0,5 to 2 per cent by weight, based on the weight of the rubber.  The preferred compounds have the formula: <FORM:0769718/V/1> wherein R is an aromatic radical having 1 to 4 substituents thereon, said substituents being selected from alkyl groups wherein at least one alkyl group has more than one carbon atom, phenyl groups, phenylalkyl groups and cycloalkyl groups, and preferably at least one substituent containing a secondary or tertiary carbon atom.  The aromatic radical may be a benzene or naphthalene ring and may be mono - di, or polyhydroxy.  Specified compositions comprise natural rubber, zinc oxide, sulphur, stearic acid and, as an antioxidant, 2(3-phthalidyl)6-t-butyl-p-cresol, 4(3-phthalidyl)6-t-butyl-o-cresol, or 3-phthalidyl-mono-t-butyl-o-iso-propyl phenol.  Other examples of the antioxidants include phthalidyl-mono-phenylethyl-p-cresols, o-phthalidyl-mono-octyl-p-cresols, phthalidyl-p-t-butyl-o-cresol, phthalidyl-p-iso-octyl phenols and phthalidyl-2, 4-di-t-butyl phenols.  (For preparation see Group IV(b)).