Note: Descriptions are shown in the official language in which they were submitted.
~L~8239~
-- 1
Case 5039/5040
.. .. .
This invention relates to 3,5-dihydrocarbyl-4-
hydroxybenzylmalonic acid esters and the preparation and
5 uses thereof as antioxidants for oxidizable organic
materials when such materials are exposed to oxidative
degradative conditions.
The materials of the invention are prepared by
reacting a 2,6-dihydrocarbyl-4-substituted-methylphenol
10 with an ester of a 1,3-dicarboxylic acid in the presence
of an alkali metal hydride or an alkaline earth metal
hydride. Thus, in one embodiment of the invention there
i8 provided a novel process for the preparation of
3,5-dihydrocarbyl-4-hydroxybenzylmalonic acid esters
15 which comprises reacting a 2,6-dihydrocarby1-4-hydroxy
or -halogen substituted-methylphenol with an ester of a
1,3-dicarboxylic acid in the presence of an alkali metal
hydride or an alkaline earth metal hydride.
Thus, in the present invention there i9 provided
20 a proce~s for the preparation of 3,5-dihydrocarbyl-4-
hydroxybenzylmalonic acid esters having the general
formula:
.
' :
.
.
I , ' ' j
.
34
- 2 -
lH
Rl~ ~R2
l~ ~ (III)
' O
S . ~ ~ OR3
O=C~
OR4
which comprises reacting a 2,6-dihydrocarbyl-4-substi-
tuted-methylpheno]. of the general formula:
L0 OH
Rl ~, R2
H2C \
with an ester of a 1,3-dicarboxylic acid of the general
15 formula:
O
R30CCH~COR4
~ .
Z~823~
in the presence of an alkali metal hydride or sn alka-
line earth metal hydride ~berein in tbe structural for-
mulas above Rl and R2 are the same or diffetent and
are hydrogen or hydrocarbyl radicals having up to at
5 least 40 carbon atoms with the provision that at least
one of Rl or R2 must be other than hydrogen; R3
and R4 are the same or different and are linear or
branched alkyl radicals having up to at least 20 carbon
atoms with the provision that at least one of R3 or
10 R4 must be other than hydrogen and Y is hydroxy or
halogen.
Representative examples of radicals described
above are secondary radicals such as secondary butyl,
secondary amyl, secondary octyl; tertiary radicals such
15 as tertiary butyl, tertiary hexyl and tertiary decyl;
alkyl radicals such as methyl, ethyl, propyl, butyl,
nonyl, decyl, tetradecyl, hexadecyl, nonadecyl; aralkyl
radicals such as methyl phenyl and pentyl phenyl, and
Z cycloalkyl radicals such as cyclopentyl, cyclohexyl and
20 cycloheptyl radicals.
Representative examples of the Group I compounds
are
2,6-di-t-butyl-4-chloroethylphenol,
2,6-di-t-butyl-4-bromomethylphenol,
2,6-di-t-butyl-4-iodomethylphenol,
2-methyl-6-isopropyl-4-chloromethylphenol,
.
.
- , .
.
, .
~2~;313Z34
-- 4 --
2-methyl-6-isopropyl-4-bromomethylphenol,
2-methyl-6-isopropyl-4-iodomethylphenol,
2-methy]-6-t-butyl-4-cbloromethylphenol,
2-methyl-6-t-butyl-4-bromomethylphenol,
2-methyl-6-t-butyl-4-iodomethylphenol,
2,6-diisopropyl-4-chloroethylphenol,
2,6-diisopropyl-4-bromomethylphenol,
2,6-diisopropyl-4-iodomethylphenol,
2-sec-butyl-4-chloromethylphenol,
2-sec-butyl-4-bromomethylphenol,
2-sec-butyl-4-iodomethylphenol,
2-isopropyl-4-chloromethylphenol,
2-isopropyl-4-bromomethylphenol,
2-isopropyl-4-iodomethyiphenol,
2-t-butyl-4-chloromethylphenol,
, 2-t-butyl-4-bromomethylphenol,
2-t-b~tyl-4-iodomethylphenol,
2-ethyl-6-t-butyl-4-chloromethylphenol,
2-ethyl-6-t-butyl-4-bromomethylphenol,
2-ethyl-6-t-butyl-4-iodomethylphenol,
2,6-diheptyl-4-chloromethylphenol, !
2',6-diheptyl-4-bromomethylphenol,
2,6-diheptyl-4-iodometbylphenol,
2-ethyl-S-methyl-4-chloromeChylphenol,
25 . 2-ethyl-6-methyl-4-bromomethylphenol,
2-ethyl-6-methyl-4-iodomethylphenol,
. , .
8;~3~
.. 5 _ .
2-t-butyl-6-heptyl-4-chloromethylphenol,
2-t-butyl-6-heptyl-4-bromomethylphenol,
2-t-butyl-6-heptyl-4-iodomethylphenol,
2-methyl-6-ethyl-4-chloromethylphenol,
2-methyl-6-ethyl-4-bromomethylphenol,
2-methyl-6-ethyl-4-iodomethylphenol,
2,6-di-t-butyl-4-hydroxymethylphenol,
2-methyl-6-isopropyl-4-hydroxymethylphenol,
2-methyl-6-t-butyl-4-hydroxymethylphenol,
2,6 diisopropyl-4-hydroxymethylphenol,
2-sec-butyl-4-hydroxymethylphenol,
2-isopropyl-4-hydroxymethylphenol,
2-t-butyl-4-hydroxymethylphenol,
2-ethyl-6-t-butyl-4-hydroxymethylphenol,
2,6-diheptyl-4-hydroxymethylphenol,
2-ethyl-6-methyl-4-hydroxymethylphenol,
2-t-butyl-6-heptyl-4-hydroxymethylphenol,
2-methyl-6-ethyl-4-hydroxymethylphenol, and
the like.
. 20 Representative examples of Group II esters of
1,3-dicarboxylic acid compounds are
malonic acid, dimethyl ester, ~ :
malonic acid, diethyl ester,
malonic acid, diisopropyl ester,
malonic acid, di-n-hexyl ester,
malonic acid, dioctyl ester,
,
~, ~ , \
3Z34
;
-- 6 --
malonic acid, didodecyl eYter,
malonic acid, ethyl, methyl diester,
malonic acid, ethyl, isopropyl diester,
malonic acid, n-butyl, ethyl diester,.
S malonic acid, n-butyl, dodecyl diester,
malonic acid, octyl, ethyl diester,
malonic acld, ethyl monoester,
malonic acid, n-propyl monoester,
malonic acid, n-butyl monoester,
malonic acid, n-hexyl monoester,
malonic acid, octyl monoester,
malonic acid, dodecyl monoester, and the like.
Representative examples of Group III benzylated
malonic acid esters functioning as antioxidants, are
lS 3,S-di-t-butyl-4-hydroxybenzylmalonic acid, ~
dimethyl ester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
diethyl ester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
diisopropyl ester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
di-n-hexyl ester,
'. 3,5-di~t-butyl-4-hydroxybenzylmalonic acid,
~ dioctyl ester,
i 25 3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
didodecyl ester,
'. .
., :, '
!
., j
';
.
_ _
, :
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~' ' ' : ' ~' '
:
-~ ~Z~823~
. 7 _
: 3,5-di t-butyl-4-hydroxybenzylmalonic acid,
ethyl, methyl diester, -`
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
ethyl, isopropyl diester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
n-butyl, ethyl diester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
n-butyl, dodecyl diester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
octyl, methyl diester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
octyl, ethyl diester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid, '
ethyl monoester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
n-propyl monoester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
n-butyl monoester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid,
n-hexyl monoester,
3,5-di-t-butyl-4-bydroxybenzylmalonic acid,
octyl monoester,
3,5-di-t-butyl-4-hydroxybenzylmalonic acid, ' ~`
.dodecyl monoester,
3-ethyl-5-ethyl-4-hydroxybenzylmalonic acid, .
dioctyl e3ter,
~ :.
,
.
. . .
`' ~ . ' :
~ lZ~3Z3~
.
- 8 -
3-n-butyl-5-octyl-4-hydroxybenzylmalonic acid,
ethyl, methyl diester,
3-ethyl-5-methyl-4-hydroxybenzylmalonic acid,
ethyl monoester,
3,5-dioctyl-4-hydroxybenzylmalonic acid,
octyl monoester, and tbe like.
In general, any of the alkali metal hydrides or
alkaline earth metal hydrides may be used in the prsc-
tice of the present process. These include sodium
10 hydride, potassium hydride, lithium hydrlde, magnesium
hydride, calcium hydride, and the like. Sodium hydride
is preferred.
The process of the invention is carried out by
reacting the 2,6-dihydrocarbyl-4-hydroxymethylphenol or
15 the 2,6-dihydrocarbyl-4-halomethylphenol starting
material with at least 1 molsr equivalent of malonic
acid ester reactant although an exces3 of ester reactant
can be used. A preferred range of malonic acid ester
reactant to halometbylphenol reactant or hydroxymethyl-
20phenol reactant is from about 1 to 10 moles of ester permole of halomethylphenol or hydroxymethylphenol reactant.
At least 1 mole of hydride per mole of halo-
methylphenol or hydroxymethylphenol reactant should be
used in the proces~ of the invention, although an amount
25 of hydride up to about 50 moles of hydride per mole of
'~ , ' ' " '
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,
3234
g
the substituted methylphenol reactant can be used, if
desired.
The reaction is advantageously conducted at a
temperature of from 50C. to 500C. While lower
5 temperatures can be used, the reaction rates are
generally correspondingly lower. Temperatures above
500C. can be used, but excessive decomposition of the
reaction components can occur. Reflux temperature at
atmospheric pressure is effective and preferred.
Typically, the reaction can be cooducted at
atmospberic pressure. However, higher pressures up to
about 1000 psig may be used, if desired.
i The use of a solvent for the reaction mixture is
not generally required, especially if ~n excess of
15 malonic acid ester reactant is used. However, if
desired, a solvent which is inert under the reaction
conditions, i.e., those solvents which do not enter into
the reaction, may be added to the reaction vessel.
Useful solvents comprise aprotic solvents which include
20 ethers ~uch as diethyl ether, dibutyl ether, l-ethoxy-
hexane, tetrahydrouran, 1,4-dioxane, 1,3-dioxolane,
diglyme, 1,2-diethoxyethane, and tertiary amines such
as pyridine, N-ethylpiperidine, triethylamine, tributyl-
amine, N,N-diphenyl-N-methylamine, N,N-dimethylalanine,
25 etc. Especially useful solvents are dipolar aprotic
solvents such aa dimethyl sulfoxide, N,N-dimethylforma-
,
' i i:
., ! .
r
. .
'
- , '
i2~3Z34
- ld -
mide, N,N-dimethylacetamide, dimethyl sulfone, tetra-
methylene sùlfone, N-methy~lpyrrolidinone, acetonitrile
and like materials. Other solvents which are inert
under the reaction conditions may be used: for example,
5 low boiling hydrocarbons, halogenated hydrocarbons,
examples of which are benzene, tolueoe, tetrachloro-
ethane, the chlorinated benzenes, the chlorinated
toluenes, etc., and lower alkanols having up to about 6
carbon atoms. These include methanol, ethanol, n-pro-
10 panol, igopropyl alcohol, n-butanol, sec-butyl alcohol,
t-butyl alcohol, n-pentanol, isopentyl alcohol,
n-hexanol and isohexyl alcohol.
The amount of solvent can be expressed as a
volume ratio of ~olvent to halomethylphenol reactant or
15 hydroxymethylphenol r3actant. Suitable volume ratios of
solvent to halomethylphenol reactsnt or hydroxy-
methylphenol reactant can be from 0/1 to 500/1 and
preferably from 1/1 to 300/1.
The mode of addition in the process i9 not par-
20 ticularly critical. Accordingly, it i9 convenient toadd the halomethylphenol reactant or the hydroxymethyl-
phenol reactant to a mixture of the other materials, add 1`
the malonic acid ester compound to a mixture of the
other material~, add the reactants to a mixture of the
25 substituted methylphenol and solvent, introduce all
:
.
. I , ' .
' . ' ' `
.
~Z~ 34
11 -
ingredients simultaneously into the reaction zone, or
the like.
The process should be carried out for the time
sufficient to convert substantially all of the halo-
methylphenol reactant or the hydroxymethylphenol to the
corresponding benzylated malonic acid ester. The length
of time for optimum yield will depend primarily upon the
reaction temperature and the particular solvent, if any,
used in the reaction. In general, excellent yields
of the benzylated malonic acid ester are obtained in
from about two to twenty-four hours.
Although not required, the process can be con-
ducted irl a substantially anhydrou~ reaction system, and
accordingly, the components of the reaction system are
brought together and maintained under a substantially
dry, inert atmosphere. hy "substantially anbydrous" is
meant a reaction system wherein the total amount of
water present is no more than about 5 percent by weight,
based on the reaction mixture. When the amount of water
in the system exceeds this, both reaction rate and yield
oE product decrea~e.
The process may readily be conducted in a batch-
wise, semi-batch or continuous manner and in conven-
tional equipment.
Under the reaction conditions, elimination of the
hydroxyl group or hnlide occurs yieldlng a quinone
. .
, .
' ~ .
,`
~L2C~Z34
- 12 -
methide intermediate which undergoes nucleophilic attack
by the malonic acid ester leactant to form the desired
benzylated malonic acid ester product. Some bis-
hydroxyphenyl)methane and benzyl ether by-products may
5 also be formed.
The benzylated malonic acid ester product is
easily separated from the reaction mixture by such means
as distillation, extraction, crystallization and other
methods obvious to tbose skilled in the chemical pro-
10 cessing art.
The benzylated malonic acid ester products pre-
pared by the process of this invention have antioxidant
properties and are capable of stabilizing polymers nor-
mally subject to oxidative degradation when incorporated
into the polymers using conventional techniques such as
by addition to polymer lattices; or by addition to solid
polymers on a mill or in a Banbury. Further, the novel
compounds of this invention are effective antioxidants
in both unleaded and leaded gasolines made from a wide
20 variety of base stocks and for engine and industrial
oils which are derived from crude petroleum or produced
synthetically.
The practice of this invention will be still
further apparent by the following illustrative examples.
..~
3g~
- 13 -
Example I
A dimethylformamide solution (25 mmols) of j
diethyl sodiomalonate (generated by treating a dimethyl-
formamide solution of 2.4 g; 15 mmols diethyl malonate
5 with 0.72 g; 30 mmols oil-free sodium hydride) was added
with stirring under a nitrogen atmosphere to a dimethyl-
formamide solution (25 mLs~ oi 2,6-di-t-butyl-4-chloro-
methylphenol (2.49 g; 10 mmols). The reaction mixture
was heated to a temperature of 125C and held at that
10 temperature for 3 hours nnd then poured into cold 2N
hydrochloric acid (100 mLs). The aqueous reaction r
slurry was extracted with dietbyl ether (3 x 30 mLs).
The combined organic extract was dried (MgS04) and
concentrated to give 2.44 g; 39% by VPC of 3,5-di-t-
15 butyl-4-hydroxybenzylmalonic acid, diethyl ester.
Example II
To an ethanol solution (10 mLs) of 2,6-di-t-
butyl-4-hydroxymethylphenol (2.63 g; 10 mmols) and
ethanol solution (15 mmols) of diethyl sodiomalonate
20 (generated by treating an ethanol solution of 1.6 g; 10
mmols diethyl malonate with 0.48 g; 20 mmols oil-free
sodium hydride) was added with stirring under a nitrogen
atmosphere. The reaction mixture was heated at reflux
for 16 hours and then poured into cold 2N hydrochloric
25 acid (100 mLs). The aqueous reaction slurry was ex-
I tracted with diethyl ether (3 x 30 mLs). The combined
.1 . i
I
,
~ ~21D~Z3~
- 14 -
organic,extract was dried (MgS04) and concentrated to
give 1.42 g; 39% by VPC of.3,5-di-t-butyl-4-hydroxy~-
benzylmalonic scid, ethyl ester.
'.
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