GB1561311A - Hindered phenol and their use as antioxidants - Google Patents

Description

SPECIFICATION NO 1561311 The following amendments were allowed under Section 29 on 2 March 1981.

Page 1, lines 6,26 and 37, Page 2, lines 1,59 and 63, Page 3, line 17, delete novel Page 1, line 29, delete novel insert processes of preparing Page 1, line 36, after radical insert, as well as compounds of formula II per se Page 6, line 24, Formula delete

Page 7, lines 1 and 2, delete each of R, and R2 represents hydrogen, a Cl-C4 alkyl radical or an Ar radical, Page 7, delete lines 4 and 5 Page 7, for claims 3 to 8,10 to 12 and 15 to 21, read 2 to 7,8 to 10 and 11 to 17 Page 7, line 8, delete the compound of Claim 1, insert a compound having the following general formula:

where Ar represents a 3,5-di-tertiarybutyl-4-hydroxybenzyl radical, each of Rl and R2 represents hydrogen, a Cl to C4 alkyl radical or an Ar radical as described above, or

where Ar is as previously described and R3 represents a Cl to C4 alkyl radical, or a methoxy or ethoxy substituted Cl to C4 alkyl radical, Page 7, line 20, for 4 read 3 Page 7, lines 22 and 26, for 4 or 5 read 3 or 4 Page 7, line 24, for 4 to 6 read 3 to 5 Page 7, delete lines 28,32 and 33 Page 7, lines 46 and 47, delete 4 to 8 and 15 to 20 insert 3 to 7 and 11 to 16 THE PATENT OFFICE 27March 1981 Bas 82000/8

where : r represents a 3,5-di-tertiarybutyl-4-hydroxybenzyl radical, each of R, and R. represents hydrogen, a C, to C, alkyl radical or an Ar radical as described above, and

where Ar is as previously described and R3 represents a Cl to C, alkyl radical, or a methoxy or ethoxy substituted Cl to C4 alkyl radical.

The novel compounds of the present invention have a relatively low volatility and high molecular weight, when compared to conventional phenolic antioxidants.

(54) HINDERED PHENOLS AND THEIR USE AS ANTI-OXI DANTS (71) We, FMC CORPORATION, a Corporation organised in the State of Delaware, United States of America, of 2000 Market Street, Philadelphia, Pa. 19103, United States of America, do hereby declare the invention, for which we pray rhnt a Datent may be granted to us, and the method by which it is to be performed, @ by the following statement:

ERRATUM Slip No 2 SPECIFICATION NO 1561311 Page6, line 18, Table 1, delete existing formula, insert (CH,), C CH2 HO-CHzO-i=C-CH= C(CH3) 3 'CCH THE PATENT OFFICE I I Jtitie 1981 Bas 83361/1 r the present invention, nor is tnere u....- employing the nitroalkane based hindered phenol antioxidants as described nerciii.

In accordance with the present invention, there are provided novel hindered phenolic compounds having the following general formulas:

where. Ar represents a 3,5-di-tertiarybutyl4-hydroxybenzyl radical, each of R, and Rs represents hydrogen, a Cl to C, alkyl radical or an Ar radical as described above, and

where Ar is as previously described and Rs represents a C, to C ; alkyl radical, or a methoxy or ethoxy substituted Cl to C4 aLtcvl radical.

The novel compounds of the present invention have a relatively low volatility and high molecular weight, when compared to conventional phenolic antioxidants.

(54) HINDERED PHENOLS AND THEIR USE AS ANTI-OXIDANTS (71) We, FMC CORPORATION, a Corporation organised in the State of Delaware, United States of America, of 2000 Market Street, Philadelphia, Pa. 19103, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement :- This invention relates to novel di-tertiary-butyl substituted phenols, or hindered phenols, which are highly effective antioxidants, and to processes for obtaining these phenols from reactions with a nitroalkaue.

Phenolic antioxidants are commonly employed as stabilizers for a wide variety of organic substrates including natural and synthetic rubber, petroleum products such as lubricants, synthetic organic functional fluids, and polymers and plastics such as polyolefins and polyvinyl chloride. These phenolic antioxidants are generally the hindered phenols, that is, phenols containing alkyl substituents, as exemplified by 2,6-di-t-butyl-áesol, the alkyl-p-amino phenols and 4,4'-butylidene bis (6-t- butyl-m-cresol).

Improved phenolic antioxidants are continually in demand, particularly improved antioxidants which are effective under conditions of extended use or high tempera tures, such as are encountered in petroleum oils and lubricants, hydraulic fluids, plastics and rubber, where the volatility of conventionally employed lower molecular weight materials is a disadvantage. It is an object of the present invention to pro vide relatively high molecular weight improved hindered phenolic antioxidants with a high degree of stabilizer activity.

Phenolic resins based on the reaction of phenol itself, formaldehyde and nitro paraffins are known and are described, for example, in U. S. Patents 2,531,863 issued November 28,1950, and 2,760,951, issued August 28,1956. However, the prior art fails to teach or suggest the novel compounds prepared in accordance with the present invention, nor is there any disclosure of the advantage obtainable in employing the nitroalkane based hindered phenol antioxidants as described herein.

In accordance with the present invention, there are provided novel hindered phenolic compounds having the following general formulas:

where Er represents a 3,5-di-tertiarybutyl-4-hydroxybenzyl radical, each of Ri and R, represents hydrogen, a C, to C, alkyl radical or an Ar radical as described above, and

where Ar is as previously described and R3 represents a C, to C alkyl radical, or a methoxy or ethoxy substituted Cl to C4 alkvl radical.

The novel compounds of the present invention have a relatively low volatility and high molecular weight, when compared to conventional phenolic antioxidants.

The novel compounds of the present invention may be prepared by a number of suitable techniques. As described herein after, a nitroalkane may be reacted with formaldehyde and 2,6-di-t-butylphenol or a nitroalkane may be reacted with an intermediate, a 3,5-di-t-butyl-4-hvdroxybenzyl N, N-dialkyl dithiocarbamate. A third technique is to condense a nitroalkane with a 4-alkoxymethyl-2, 6-di-t-butylpheno (. Nitro- methane, nitroethane and both 1-and 2-nitropropane are particularly preferred reactants.

Suitable but less preferable techniques also include condensation reactions between a nitroalkane and other substituted derivatives of 4-methyl-2,6-di-z-butylphenol, the substituent replacing one or more of the hydrogens in the 4-methyl group and being selected from the group consisting of halogen, alkylamino, hydroxy and thioalkyl.

The preferred techniques for preparing the compounds of the present invention are novel processes and, as such, constitute further embodiments of the present inven tion. In a process according to the invention, a selected nitroalkane is reacted in the presence of a polar, water miscible organic solvent and, optionally, a basic catalyst at room temperature up to the reflux temperature of the organic solvent. The reaction mixture is refluxed in an inert atmosphere for a period of about 1 to 25 hours and, at the completion of the reaction and cooling of the reaction mixture, the product crystallizes. In one embodiment, 2 or 3 moles of 2,6-di-t-butylphenol and 2 or 3 moles of formaldehyde are condensed with 1 mole of a secondary nitroalkane to obtain compound (I) or a primary C2-C4 nitroalkane to obtain compound (II).

An altemate preferred procedure is first to prepare a 3,5-di-t-butyl-4-hydroxybenzvl N, N-dialkyldithiocarbamate. This intermediate is known as described, for example, in U. S. Patents 3,260,756 and 3,260,758, both issued July 12,1966, as well as in U. S. Patent 3,117,947, issued January 14,1964. The dietliyldithiocarbamate is reacted with the desired nitroalkane in a molar ratio of 1 to 3 moles per mol of nitroalkane, the nitroalkane being nitromethane to obtain compound fI) and a primary C2C4 nitroalkarie being selected to produce compound II).

The third preferred procedure to produce compound (I) is to react a nitroalkane, such as nitromethane, with about 1 to 3 moles of a 2,6-di-t-butyl-4-lower-alkoxymethylphenol, wherein the alkoxy may have up to about 4 carbon atoms and preferably is methoxy or ethoxy. The reaction is preferably carried out at the reflux temperature of the solvent and the product is obtained in a form of solid crystals.

The compounds represented by Formula I are prepared by the reaction of nitromethane with either the described diethyldithiocarbamate or with a 2,6-di-t-butyl4-lower-alkoxymethylphenol, or by the reaction of a secondary nitroalkane, such as 2-nitropropane, with formaldehyde and 2,6-di-t-butylphenol.

The nitronates as represented by Formula II are prepared by the reaction of a primary nitroalkane, except nitromethane, with either formaldehyde and 2, 6-di-Z- butylphenol or with the diethyldithiocarbamate, or by the reaction of nitromethane with formaldehyde, an aliphatic (Ci-~3) alcohol and 2,6-di-t-butylphenol.

The reaction generally takes place in a temperature range from about 25 to 100 C. Suitable solvents include the lower alkanols such as methanol, ethanol, propanol, isopropanol, as well as dimethyl sulphoxide, dioxane, tetrahydrofuran, and similar organic solvents. Methanol is particularly preferred. These reactions may be carried out in the presence of a basic catalyst such as an alkali metal or alkaline earth metal or ammonium oxide, carbonate or hydroxide, particularly sodium or potassium hydroxide. The amount of base used may vary from very minor catalytic amounts up to equimolar amounts or amounts substantially in excess of equimolar amounts. Other Bronsted bases are suitable. Exact amounts will depend on the particular reaction being employed. In some cases, the base may be functioning not only as a catalyst but also as a reactant. The use of molar excesses has not been found detrimental to the reaction technique and may be required in order to insure completion of the reaction. Generally speaking, about 1 to 150 by weight of the base catalyst, based on the weight of nitroalkane, may be employed. When the base is functioning only as a catalyst, the preferred quantity used is 2 to 10 ; y by weight, based on the weight of nitroalkane.

The novel compounds of the present invention are generally useful as antioxidants for stabilization of a wide variety of organic substrate materials, and are particularly suitable for use where service temperatures are relatively high or under other conditions wherein losses of more volatile antioxidants can occur. Thus, the novel compounds of the present invention may be used as stabilizers for natural rubber and synthetic rubbers such as polybutadiene rubber, styrene-butadiene rubber, polyisoprene rubber, neoprene rubber, buryl rubber, nitrile rubber, chloroprene rubber, and ethylene-propylene-diene rubbers. The compounds are also suitable for stabilization of polyolefins such as polyethylene, polypropylene, polybutene, polymethylbutene, polypentene, and copolymers of these olefin monomers such as ethylenepropylene copolymers and polymers of other polymerizable liquid ethylenically unsaturated monomers. Other plastics and resins which may be stabilized employing the compounds of the present invention include polystyrene, polyacrylates, polycarbonates, polyesters such as polyethylene terephthalate, polyvinyl chloride, polyvinyl acetate, polyamides, polyamines, polyacrylonitrile and similar polymers which are normally subject to oxidative deterioration.

Synthetic lubricants may also be stabilized and these include alkyl oxalates and malonates, as well as polyol esters such as pentaerythritol, trimethylolpropane and sorbitol esters, alkyl esters of fatty acids such as lauric, oleic, palmitic, and stearic acids. Other synthetic lubricants and fluids include the polysiloxane oils, fluorocarbon lubricants, polyalkylene glycol lubricants such as copolymers of ethylene oxide and propylene oxide as well as triaryl phosphate ester functional fluids and lubricants.

Petroleum derived oils, fluids and lubricants may also be stabilized employing the novel antioxidants of the present invention and these organic substrates include industrial oils, turbine oils, transmission fluids, transformer oils and mineral oils, as well as fuels such as gasoline, jet fuel, diesel fuel and kerosene.

The compounds of the present invention are particularly suitable for the stabilization of polyolefin polymers, particularly polypropylene, and for the stabilization of synthetic rubbers, The compounds of the present invention are generally employed in amounts ranging from 0.001 to 5 parts by weight per 100 parts of the organic materials being stabilized. Conventional techniques are employed to add the antioxidants to the organic substrate, such as mixing or milling or use of a mutual solvent.

The invention is further illustrated by the following Examples which should not be considered as limitative of its scope. The structure of all compounds was confirmed by IR and NMR spectroscopy. Temperatures reported are in degrees centigrade and percentages are by weight, unless otherwise stated.

Example I Preparation of Tris- (3, 5-di-t-butyl-4-hydroxybenzyl) nitromethane.

To a rapidly stirred solution of 11.01 g of 3,5-di-t-butyl-4-hydroxybenzyl N, Ndiethyldithiocarbamate in 100 ml of hot methanol was added a freshly prepared solution of 1.68 g of potassium hydroxide and 0.61 g of nitromethane. The resulting stirred mixture was refluxed under nitrogen for 24 hours. Upon cooling, 3.0 g of the product precipitated as white crystals, mp 199-201 C. An additional 2. 07 g of pure product was obtained from the filtrate after recrystallization from acetonitrile and vacuum drying.

Elemental Analysis: Calcd. for CHe. NO. : %C, 77.17 ; % H, 9.72; u/N, 1.96.

Found: % C, 77.05; % H, 9.90; oN, 2.12.

Example II Preparation of 3,5-di-t-butyl-4-hydroxybenzyl 1- (3, 5-di-t-butyl-4-hydroxybenzyl)-3- methoxypropane-2-nitronate.

2,6-di-t-butylphenol, 30. 3 g, in SO ml of methanol, was added at room temperature to a stirred solution of 24.3 g of 37% aqueous formaldehyde in 50 ml of methanol. A freshly prepared solution of 2.8 g of potassium hydroxide and 3.05 g of nitromethane was subsequently added. The resulting stirred solution was refluxed under nitrogen for 24 hours and kept at room temperature for 96 hours. The product, 5. 2 g, mp 218-220 C., was collected and washed with cold methanol and was recrystallized from acetonitrile and finally washed with hexane to obtain white crystals, mp 221-2 C.

Elemental Analysis: Calcd. for CHNO, : %C, 72.76; c/),, H, 9.44 ; N, 2.56.

Found : %C, 73.16; 'H, 9. 49; 0,', N, 2.59.

Example III Preparation of 3,5-di-t-butyl-4-hydroxybenzyl 1-(3, 5-di-z-butyl-4-hydroxybenzyl,- butane-2-nitronate.

(a) To a stirred solution of 20.6 g of 2,6-di-t-butylphenol and 16.2 g of 37 aqueous formaldehyde (excess) in 75 ml of methanol was added at 25"C a freshly prepared solution of 4.5 g of nitropropanc and 2.8 g of potassium hydroxide in 50 ml of methanol. The resulting stirred mixture was refluxed under nitrogen for 18 hours. A precipitate was observed to form after 35 minutes. The mixture was cooled in ice water and the crude product collected, mp 170-8C, and recrystallized from acetonitrile to yield 17.0 g of pure product, mp 176-178'C.

(b) 3,5-di-t-butyl-4-hydroxybenzyl N, N-diethyl-dithiocarbamate, 7.34 g in 100 ml of warm ethanol containing 0.89 g of nitropropane was treated with 1.17 g of KOH in 100 ml of warm ethanol. The resulting stirred solution was refluxed under nitrogen for 16 hours. The reaction mixture was concentrated and extracted with hexane from which was obtained, after initial precipitation of a salt, 2.35 g of product. Two recrystallizations from acetonitrile afforded the product, mp 177 180 C., identical to that obtained by procedure (a).

Elemental Analysis: Calcd. for C33H51NO4: %C, 75.38; %H, 9.78 ; %N, 2.66.

Found : %C, 75. 34 ; %H, 9.74; zNw 3.26.

Example IV Preparation of 3,5-di-t-butyl-4-hydroxybenzyl 1- (3, 5-di-t-butyl-4-hydroxybenzyl)- propane-2-nitronate.

To a stirred solution of 2,6-di-t-butylphenol, 20.6 g, and 37",, aqueous formaldehyde, 16.2 g (excess), in 100 ml of methanol was added a freshly prepared solution of 5. 6 g of potassium hydroxide and 3.75 g of nitroethane in 7S ml of methanol The reaction mixture was heated to reflux under nitrogen for 17 hours. A precipitate began to form after one hour. The product was collected and washed with cold methanol giving 17. 3 g of pure product, mp 20S-210 C.

Elemental Analysis: Calcd. for C32H49O4N: %C, 75. 10 ; %H, 9.65, ;, N, 2. 74.

Found : %C, 75. 32 ; %H, 9.82; I) N, 2. 68.

Example V Preparation of 2,6-di-t-butyl-4- (2-methyl-2-nitropropyl) phenol.

2,6-di-t-butylphenol, 20.6 g, in 100 ml of stirred methanol containing 16.2 g of 37% aqueous formaldehyde (excess) was treated with a freshly prepared solution of 5. 6 g of potassium hydroxide and 8.9 g of 2-nitropropane and heated under nitrogen for 2-1/2 hours. Upon cooling, 19.8 g of product, mp 1014-C. was obtained in two crops. Recrystallization from methanol afforded product melting 103.5-105. 5 C.

Elemental 7 Calcd. for CH.,., NO, : %, C, 70. 32 ; ;. H, 9.51,,. o, 4. 6.

Found : %C, 70.60 ; %H, 9.41 z 4.49.

Example VI Preparation of 1, 3-bis (3,5-di-t-butyl-4-hydroxyphenyl)-2-nitropropane.

To a solution of 14.5 g (0.22 mole) of 85''potassium hydroxide in 300 ml of methanol was added in a stream of nitrogen to exclude air 13. 4 g (0. 22 mole) of nitromethane and 50. 0 g (0.2 mole) of 2, 6-di-t-butyl-4-methoxy-methoxyphenol. The magenta solution was stirred for one hour at reflux, with exclusion of air. After cooling somewhat, the solution was neutralized with 13 ml of acetic acid and chilled.

A thick paste formed with was filtered, washed and dried. The resulting un powder (48. 1 g, mp 152-154 C) was recrystallized from 500 ml of heptane, atter hlterillg insoluble matter (10. 4 g). The yield of tan crystals was 32.3 g, mp 161-163 C Elemental Analysis: Calcd. for C31H47NO@: %C, 74.81, @H, 9.42, N, 2,82.

Found: C. 74.80 : H, 9.92 ;, 2.73.

Example VII The use of these compounds as antioxidants is demonstrated by the AST. N1 D943 oxidation test for turbine oils. The results are set out in Table 1 TABLE 1 Hours to Compound Conc. Failure Blank < 125 Tris- (3, 5-di--butyl---hydroxybenzyly nitromethane 0. 5 2,051 3,5-di-t-butyl-4-hs droxybenzyl 1-(3, 5-di-t-butyl-4 hydroxybenzyl) propane-2-nitronate 0. 5 1,419 3,5-di-t-butyl-4-hydroxybenzyl 1- (3, 5-di-t-butyl-4 hydroxybenzyl) butane-2-nitronate 0.1 > 400 2,6-di-t-butyl-4- (2-methyl-2-nitropropyl) phenol 0.1 > 400 3,5-di-t-butyl-4-hydroxybenzyl 1- (3, 5-di-t-butyl-4- hydrox) benzyl)-3-methoxypropane-2-nitronate 0.1 > 400 Example VIII The usefulness of the compounds of this invention as antioxidants in a triaryl phosphate Quid is demonstrated in this Example. A commercial triaryl phosphate, Kronitex 100 (Registered Trade Mark) (FMC Corp.), a mixed isopropylphenyl/ phenyl phosphate produced by phosphorylation of phenol alkylated with about 30 do by weight propylene containing 0.1'',, of two representative compounds of this invention was evaluated via the ASTM D2272 Rotary Bomb Oxidation Stabiliy Test. The induction period is a measure of the rate of oxygen consumption in a sealed, pressurized bomb. The results are as follows: Induction Period Compound (minutes) Blank 94 Tris- (3, 5-di-t-buryl-4-hydroxybenzyl) nitromethane 240 3,5-di-t-butyl-4-hydroxybenzyl 1- (3, 5-di-t-butyl-4-hydroxy- benzyl) propane-2-nitronate 235 Example IX The compounds of Example VIII were shown via the ASTM D2272 Rotary Bomb Oxidation Stability Test ro impart enhanced oxidative stability when added to a commercial uninhibited 5 centistoke synthetic ester lubricant (pentaerythritol ester of mixed C-,-C,, carboxylic acids).

Example X In order to demonstrate the effectiveness of the antioxidants of this invention in improving the oxidation stability of polypropylene"Oven Aging Test"were conducted in an air circulating oven maintained at 150 C. Samples of unstabilized polypropylene homopolymer molding powder (Hercules Profax (Registered Trade Mark) 6401) containing the compounds of this invention alone and in combination with DLDTP (dilauryl 3,3-thiodipropionate), a synergist for hindered phenol antioxidants, were evaluated. BHT (2,6-di-t-butyl-4-methylphenol), a commercial antioxidant, was included. Five replicates of each polypropylene-stabilizer composition were prepared and the test criteria is the average time to deterioration of the five samples as evidenced by crazing on the surface.

Test specimens were prepared by mixing the polypropylene and stabilizer sysu : m in a blender followed by banding at 175 C (350 F) and fluxing at 155 C (310 F) on a two roll mill for less than ten minutes. The resulting samples were pressed at 155 C (310 F) under 11.77 to 12.46 MN. M-2 (1700 to 2800 psi) pressure into (15. 24X15. 24 cm (6X6 inch) sheets, 0.1905 mm (0.0075) inch thick.

The sheets were cut and trimmed into test specimens 2. 54 x 1.27 cm (1 x 1/2 inches).

The following Table 2 summarizes the results : TABLE 2 Oven Aging Tests Hours to Sample Antioxidant Synergist Failure (a) None None 75 (b) BHT None 15 (c) BHT DLTDP 39 (d) None DLTDP 137 (e) Ex. 1 None 143 TABLE 2 (cont.) (f) Ex. I DLTDP 359 (g) Ex. 2 None 66 (h) Ex. 2 DLTDP 303 (i) Ex. 4 None 61 (j) Ex. 4 DLTDP 215 (k) Ex. 3 None 61 (1) Ex. 3 DLTDP 153 (m) Ex. 5 None 19 (n) Ex. 5 DLTDP 42 In each sample, the antioxidant concentration was 0. 1% that of polypropylene.

When present, the synergist was used at a concentration of 0.2%. Samples (e)- (n) employed compounds of the invention and refer to compounds illustrated in Examples 1-5.

The formulas and compound names for particularly preferred embodiments of the present invention are set forth in the following Tables I and II.

Toble I

3,5-di-t-butyl-4-hydroxybenzyl 1-(3,5-di-@-butyl-4-hydroxy benzyl)-3-methoxypropane-2- nit sonate 3,5-di-t-butyl-4-hydroxybenzyl 1-(3,5-di-@-butyl-4-hydroxybenzyll-propcne-2-nitronate 3, 5-di-@-butyl-4-hydroxybenzyl 1-(3,5-di-@-butyl-4-hydroxy- benzyl)-butane-2-nitronate Table 11

2,6-di-@-butyl- 4-1 2-methyl-2nitropropyl) phenol

Tris (3,5-di-@- bulyl-4-hydroxybenzyl) mtromethane

1, 3-bis (3, 5-di @-butyl-4-hydroxyphenyl 1-2- nitropropone

Claims (21)

1. WHAT WE CLAIM IS :- 1. An antioxidant compound of the general formula

   wherein Ar represents a 3,5-di-tertiary-butyl-4-hydroxybenzyl radical, each of R, and R represents hydrogen, a C,-C, alkyl radical or an Ar radical, and R3 represents a ClC, alkyl radical or a methoxy-or ethoxy-substituted C,-C4 alkyl radical.
2. 2. An antioxidant compound of formula I according to Claim 1, wherein, Ri and R2 both represent methyl radicals or Ar radicals.
3. 3. An antioxidant compound of formula II according to Claim 1, wherein R3 represents a methyl radical, an ethyl radical or a methoxy-substituted methyl radical.
4. 4. A process for preparing the compound of Claim 1, characterized in that a nitroalkane is reacted in the presence of a polar, water miscible organic solvent at room temperature to the reflux temperature of the organic solvent with 2 or 3 moles of 2,6-di-t-butylphenol and 2 or 3 moles of formaldehyde per mole of nitroalkane, the nitroalkane being a secondary nitroalkane, to obtain, compound (I) and a primary C., -C, nitroalkane to obtain compound (II); or with 1 to 3 moles of 3,5-di-t-butyl-4hydroxybenzyl N, N-dialkyldithiocarbamate per mole of nitroalkane, the nitroalkane being nitromethane to obtain compound (I) and a primary C,,-C, nitroalkane to obtain compound (II) ; or 1 to 3 moles of 2,6-di-t-butyl-4-(C, C4) alkoxymethylphenol per mole of nitroalkane to obtain compound (I) ; or formaldehyde, 2,6-di-tbutylphenol and an aliphatic (C, C3) alcohol, the nitroalkane being nitromethane, to obtain compound (II).
5. 5. A process according to Claim 4, wherein the nitroalkane is reacted in the presence of the solvent and a basic catalyst.
6. 6. A process according to Claim 4 or 5, wherein nitromethane is reacted with the carbamate to obtain compound (I).
7. 7. A process according to any of Claims 4 to 6, wherein the carbamate is 3,5-dit-butyl-hydroxybenzyl N, N-di-ethyldithiocarbamate.
8. 8. A process according to Claim 4 or 5, wherein nitromethane and 2,6-di-t butyl-4-methoxymethylphenol are reacted to obtain compound (I).
9. 9. An antioxidant compound as described in foregoing Example I.
10. 10. An antioxidant compound as described in foregoing Example II.
11. 11. An antioxidant compound as described in foregoing Example III.
12. 12. An antioxidant compound as described in foregoing Example IV.
13. 13. An antioxidant compound as described in foregoing Example V.
14. 14. An antioxidant compound as described in foregoing Example VI.
15. 15. A process for preparing an antioxidant compound, substantially as described in foregoing Example I.
16. 16. A process for preparing an antioxidant compound, substantially as described in foregoing Example II.
17. 17. A process for preparing an antioxidant compound, substantially as described in foregoing Example III.
18. 18. A process for preparing an antioxidant compound, substantially as described in foregoing Example IV.
19. 19. A process for preparing an antioxidant compound substantially as described in foregoing Example V.
20. 20. A process for preparing an antioxidant compound, substantially as described in foregoing Example VI.
21. 21. An antioxidant whenever prepared by the process of any one of Claims 4 to 8 and 15 to 20.