Phosphonoadipic acid additives to aqueous systems

A compound or mixture of compounds of the general formula: ##STR1## in which m and n may be 0 or 1 but both cannot be 1, R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently H or CH.sub.3, X.sup.1, X.sup.2, Z.sup.1 and Z.sup.2 are independently hydrogen or straight or branched chain C.sub.1 -C.sub.4 alkyl; and the water-soluble inorganic or organic salts thereof, with the proviso that at least one of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 must be CH.sub.3, and when m and n are both 0, R.sup.2 and R.sup.3 are each methyl and R.sup.4 and R.sup.5 have their previous significance, when added to an aqueous system imparts one or more of the following beneficial effects to be treated system: (a) the corrosion of ferrous metals in contact with the system is inhibited; (b) the precipitation of scale-forming salts of calcium, magnesium, barium and strontium from the treated aqueous system is inhibited; and (c) inorganic materials present in the treated aqueous system are dispersed.

The present invention relates to new phosphonic/carboxylic acids having the 
value as additives to aqueous systems and processes for their preparation. 
According to the present invention there is provided a compound or mixture 
of compounds of the general formula: 
##STR2## 
in which m and n may be 0 or 1 but both cannot be 1, R.sup.1, R.sup.2, 
R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are independently H or CH.sub.3, 
X.sup.1, X.sup.2, Z.sup.1 and Z.sup.2 are independently hydrogen or 
straight or branched chain C.sub.1 -C.sub.4 alkyl; and the water-soluble 
inorganic or organic salts thereof, with the proviso that at least one of 
R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 must be CH.sub.3, and when m 
and n are both 0, R.sup.2 and R.sup.3 are each methyl and R.sup.4 and 
R.sup.5 have their previous significance. 
When X.sup.1, X.sup.2, Z.sup.1 or Z.sup.2 is C.sub.1 -C.sub.4 alkyl this 
may be for example methyl, ethyl, propyl, isopropyl, butyl, sec-butyl or 
tertiary butyl. 
Examples of compounds of formula I when m=1 and n=0 are as follows: 
2-methyl-2-phosphonoadipic acid 
3-methyl-2-phosphonoadipic acid 
4-methyl-2-phosphonoadipic acid 
5-methyl-2-phosphonoadipic acid 
2,4-dimethyl-2-phosphonoadipic acid 
2,3-dimethyl-2-phosphonoadipic acid 
4,4-dimethyl-2-phosphonoadipic acid 
2,4,4-trimethyl-2-phosphonoadipic acid 
2,4,4,5-tetramethyl-2-phosphonoadipic acid 
dimethyl 2-methyl-2-dimethylphosphonoadipate 
2,4-dimethyl-2-monoethylphosphonoadipic acid 
diethyl 2-diethylphosphono-2-methyl-adipate 
ethyl 5-carbomethoxy-2-diethylphosphono-4-methylpentanoate 
ethyl 5-carbomethoxy-2-diethylphosphono 2,4-dimethylpentanoate diethyl 
2-diethylphosphono-4,4-dimethyladipate 
diethyl 2-diethylphosphono-2,4,4-trimethyladipate 
Examples of compounds of formula I when m=0 and n=1 are as follows: 
3-phosphonoadipic acid 
2-methyl-3-phosphonoadipic acid 
3-methyl-3-phosphonoadipic acid 
4-methyl-3-phosphonoadipic acid 
5-methyl-3-phosphonoadipic acid 
3,5-dimethyl-3-phosphonoadipic acid 
3,4-dimethyl-3-phosphonoadipic acid 
2,5-dimethyl-3-phosphonoadipic acid 
3,5,5-trimethyl-3-phosphonoadipic acid 
2,3,5,5-tetramethyl-3-phosphonoadipic acid 
3,5,5-trimethyl-3-dimethylphosphonoadipic acid 
diethyl 3-diethylphosphonoadipate 
3,5,5-trimethyl-3-monomethylphosphonoadipic acid 
An example of a compound when m and n=0 is 
2,4,4-trimethyl-2-phosphonoglutaric acid. 
Preferred compounds of formula I are those in which X.sup.1, X.sup.2, 
Z.sup.1 and Z.sup.2 are hydrogen. More preferred compounds are those in 
which X.sup.1, X.sup.2, Z.sup.1 and Z.sup.2 are hydrogen and R.sup.1, 
R.sup.4 and R.sup.6 are hydrogen. Especially preferred compounds are those 
in which X.sup.1, X.sup.2, Z.sup.1, Z.sup.2, R.sup.1, R.sup.4 and R.sup.6 
are hydrogen and R.sup.2, R.sup.3 and R.sup.5 are methyl, namely 
2,4,4-trimethyl-2-phosphonoadipic acid, 3,5,5-trimethyl-3-phosphonoadipic 
acid and 2,4,4-trimethyl-2-phosphonoglutaric acid or mixtures thereof in 
any proportion. 
Other valuable mixtures of compounds of formula I are a mixture of 
2-methyl-2-phosphonoadipic acid and 3-methyl-3-phosphonoadipic acid, and a 
mixture of 2,4-dimethyl-2-phosphonoadipic acid and 
3,5-dimethyl-3-phosphonoadipic acid. 
A further valuable mixture consists of 3-phosphonoadipic acid of the 
present invention together with 2-phosphonoadipic acid. 
The water-soluble inorganic salts of the compounds of formula I may be the 
alkali metal salts, for example the sodium and potassium salts and the 
ammonium salts. 
The water-soluble organic salts of the compounds of formula I may be the 
salts of amines, for example, mono-, di- or triethanolamines. 
The present invention further provides a process for the preparation of a 
compound of formula I where m is 1 or 0, n is 0, R.sup.1, R.sup.2, 
R.sup.3, R.sup.4 and R.sup.5 have their previous significance and X.sup.1, 
X.sup.2, Z.sup.1 and Z.sup.2 are C.sub.1 -C.sub.4 alkyl, which comprises 
reacting a compound having the formula: 
##STR3## 
wherein X.sup.1 is C.sub.1 -C.sub.4 alkyl, m is 1 or 0 and R.sup.1, 
R.sup.2, R.sup.3 and R.sup.4 have their previous significance, with a 
trialkylphosphonoacetate having the formula: 
##STR4## 
wherein X.sup.2, Z.sup.1 and Z.sup.2 are C.sub.1 -C.sub.4 alkyl in the 
presence of a condensation catalyst, conveniently a mixture of titanium 
tetrachloride and a tertiary amine such as N-methylmorpholine, to give an 
olefin having the formula: 
##STR5## 
followed by catalytic hydrogenation to give a compound having the formula: 
##STR6## 
and optionally methylating compound (V) in the presence of a base to give 
a compound having the formula: 
##STR7## 
where, in the compounds of formulae IV, V and VI, X.sup.1, X.sup.2, 
Z.sup.1 and Z.sup.2 are C.sub.1 -C.sub.4 alkyl and R.sup.1, R.sup.2, 
R.sup.3, R.sup.4 and m have their previous significance. 
The methylating agent may be, for example, dimethyl sulphate or a methyl 
halide such as methyl iodide and the base is conveniently sodium hydride. 
Subsequent hydrolysis of Compound V or Compound VI with aqueous acid or 
base gives the compounds of formula I in which m is 1 or 0, n is 0, 
R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 have their previous 
significance and at least one of X.sup.1, X.sup.2, Z.sup.1 or Z.sup.2 is 
hydrogen. The water soluble inorganic or organic salts may be obtained by 
neutralisation or partial neutralisation of these acids. 
The present invention further provides a process for the preparation of a 
compound of formula I where m is 1, n is 0, R.sup.2 is hydrogen, R.sup.1, 
R.sup.3, R.sup.4 and R.sup.5 have their previous significance, and 
X.sup.1, X.sup.2, Z.sup.1 and Z.sup.2 are C.sub.1 -C.sub.4 alkyl, which 
comprises reacting a substituted alkyl halide having the formula: 
##STR8## 
wherein X is bromo- or chloro-, X.sup.1 is C.sub.1 -C.sub.4 alkyl and 
R.sup.1, R.sup.3 and R.sup.4 have their previous significance, and the 
anion formed by treating a compound having the formula 
##STR9## 
wherein X.sup.2, Z.sup.1 and Z.sup.2 are C.sub.1 -C.sub.4 alkyl and 
R.sup.5 has its previous significance with a strong base such as sodium 
ethoxide to give a compound having the formula: 
##STR10## 
followed by catalytic hydrogenation to give a compound having the formula: 
##STR11## 
where, in the compounds of formulae IX and X, X.sup.1, X.sup.2, Z.sup.1 
and Z.sup.2 are C.sub.1 -C.sub.4 alkyl and R.sup.1, R.sup.3, R.sup.4 and 
R.sup.5 have their previous significance. 
Subsequent hydrolysis of the compound of formula X with aqueous acid or 
base gives the compounds of formula I in which m is 1, n is 0, R.sup.2 is 
hydrogen, R.sup.1, R.sup.3, R.sup.4 and R.sup.5 have their previous 
significance and at least one of X.sup.1, X.sup.2, Z.sup.1 or Z.sup.2 is 
hydrogen. The water soluble inorganic or organic salts may be obtained by 
neutralisation or partial neutralisation of these acids. 
The present invention further provides a process for the preparation of a 
compound of formula I when m is 0, n is 1, R.sup.2, R.sup.3, R.sup.4, 
R.sup.5, R.sup.6, X.sup.1 and X.sup.2 have their previous significance and 
Z.sup.1 and Z.sup.2 are C.sub.1 -C.sub.4 alkyl which comprises reacting an 
olefin having the formula: 
##STR12## 
wherein X.sup.1 and X.sup.2 are hydrogen or C.sub.1 -C.sub.4 alkyl and 
R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 have their previous 
significance, with a compound having the formula: 
##STR13## 
wherein Z.sup.1, Z.sup.2 and Z.sup.3 are C.sub.1 -C.sub.4 alkyl to give a 
compound having the formula: 
##STR14## 
wherein R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, X.sup.1 and X.sup.2 
have their previous significance and Z.sup.1 and Z.sup.2 are C.sub.1 
-C.sub.4 alkyl. 
Compounds of formula XI can be made by conventional methods. 
Subsequent hydrolysis of compound XIV with aqueous acid or base gives the 
compounds of formula I in which m is 0, n is 1, R.sup.2, R.sup.3, R.sup.4, 
R.sup.5 and R.sup.6 have their previous significance and at least one of 
X.sup.1, X.sup.2, Z.sup.1 or Z.sup.2 is hydrogen. The water soluble 
inorganic or organic salts may be obtained by neutralisa- or partial 
neutralisation of these acids. 
The present invention further provides a process for the preparation of the 
compounds of formula I wherein m, n, R.sup.1, R.sup.2, R.sup.3, R.sup.4, 
R.sup.5, R.sup.6, Z.sup.1 and Z.sup.2 have their previous significance and 
X.sup.1 and X.sup.2 are hydrogen, by oxidation of a substituted 
cyclohexanone having the formula: 
##STR15## 
wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, Z.sup.1 and 
Z.sup.2 have their previous significance. 
The compounds of formula XV are prepared by methods well known in the 
organophosphorus literature, e.g. by base catalysed addition of a dialkyl 
phosphite to the appropriate cyclohex-2-enone. 
Suitable oxidising agents are, for example, concentrated nitric acid, 
chromic acid/sulphuric acid mixtures, sodium hypochlorite, sodium 
hypobromite, hydrogen peroxide, peracetic acid and oxygen in the presence 
of a transition metal catalyst for example cobalt or manganese acetates. 
When nitric acid is used as the oxidising agent mixtures of compounds of 
formula I are usually formed in varying proportions and the individual 
components may, if desired, be isolated by conventional processes such as 
fractional crystallisation. 
By suitable selection of the conditions under which the oxidation takes 
place, the proportions of the individual components may be varied. 
In this process, when R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, 
Z.sup.1 and Z.sup.2 are all hydrogen, 3-phosphonoadipic acid of this 
invention is formed together with 2-phosphonoadipic acid. 
The oxidation with nitric acid may conveniently be carried out using from 
20% to 70%, preferably from 40% to 70% aqueous nitric acid at a 
temperature from 0.degree. to 120.degree. C., preferably from 50.degree. 
C. to 70.degree. C., advantageously in the presence of an oxidation 
catalyst such as a vanadium, manganese or copper compound. 
When oxidising a compound of formula XV wherein Z.sup.1 and Z.sup.2 are 
C.sub.1 -C.sub.4 alkyl with nitric acid, a suitable solvent may be added 
to aid solubilisation, for example, acetic acid. 
The acids formed in this process may be converted to the esters of formula 
I in which X.sup.1, X.sup.2, Z.sup.1 and Z.sup.2 are C.sub.1 -C.sub.4 
alkyl by treatment with an esterifying agent e.g. a trialkyl orthoformate. 
The compounds of formula I or salts thereof have been found to impart 
beneficial properties to aqueous systems to which they are added. 
The present invention therefore provides a method of treating an aqueous 
system which comprises adding to the aqueous system a minor proportion of 
a compound or mixture of compounds of formula I or their water soluble 
salts. The amount of compound or mixture of compounds of formula I is 
conveniently from 0.1 to 1000 parts, preferably 1 to 1000 parts and most 
preferably 1 to 50 parts by weight per million parts by weight of aqueous 
system. 
The addition of a compound of formula I, or a water-soluble salt thereof, 
to an aqueous system, has been found to impart one or more of the 
following beneficial effects to the treated system: (a) the corrosion of 
ferrous metals in contact with the system is inhibited; (b) the 
precipitation of scale-forming salts of calcium, magnesium, barium and 
strontium from the treated aqueous system is inhibited; and (c) inorganic 
materials present in the treated aqueous system are dispersed. 
The compounds of formula I may be used alone or in conjunction with other 
compounds known to be useful in water treatment. Corrosion inhibitors may 
be used such as, for example, water soluble zinc salts; phosphates; 
polyphosphates; phosphonic acids and their salts for example 
acetodiphosphonic acid, nitrilotris methylene phosphonic acid and 
methylamino dimethylene phosphonic acid; phosphonocarboxylic acids and 
their salts, for example, those described in DT-OS No. 2632774.2, and 
3-phosphonobutane 1,2,4-tricarboxylic acid; chromates, for example, sodium 
chromate; nitrites, for example, sodium nitrite; nitrates, for example 
sodium nitrate, benzotriazole, bis-benzotriazole or copper-deactivating 
benzotriazole derivatives; N-acyl sarcosines; triethanolamines; fatty 
amines; and polycarboxylic acids, for example, polymaleic acid and 
polyacrylic acid as well as their respective alkali metal salts. 
Dispersing and/or threshold agents may be used, such as for example 
polymerised acrylic acid and its salts, hydrolysed polyacrylonitrile, 
polymerised methacrylic acid and its salts, polyacrylamide and co-polymers 
thereof from acrylic and methacrylic acids, lignin sulphonic acid and its 
salts, tannin, naphthalene sulphonic acid/formaldehyde condensation 
products, starch and its derivatives, and cellulose. Specific threshold 
agents such as for example, hydrolysed polymaleic anhydride and its salts, 
alkyl phosphonic acids, 1-aminoalkyl, 1,1-diphosphonic acids and their 
salts and alkali metal polyphosphates, may also be used. 
Compounds of formula I may also be used with precipitating agents such as 
alkali metal orthophosphates, carbonates and hydroxides; oxygen scavengers 
such as alkali metal sulphites and hydrazine; sequestering agents such as 
nitrilotriacetic acid and their salts and ethylene diamine tetraacetic 
acid and its salts; antifoaming agents such as distearylsebacamide, 
distearyl adipamide and related products derived from ethylene oxide 
condensations; silicones; and fatty alcohols, such as capryl alcohols and 
their ethylene oxide condensates. 
Biocides may be used such as chlorine, ozone, acrolein, organo sulphur 
compounds for example methylene bis thiocyanate; dithiocarbamates; 
chlorinated phenols and bisphenyls, for example, 
2,2'-dihydroxy-5,5'-dichloro-diphenyl methane and pentachlorophenol; 
organometallic compounds for example tri-butyl tin oxide; and quaternary 
ammonium compounds. 
When the compound of formula I used is 3-phosphonoadipic acid, it may 
conveniently be used in admixture with 2-phosphonoadipic acid, which 
mixture is formed by the oxidation of the substituted cyclohexanone of 
formula XV, wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6, 
Z.sup.1 and Z.sup.2 are each hydrogen. 
The compounds of formula I could find use in e.g. cooling water systems; 
steam generating plant; sea-water evaporators; and hydrostatic cookers.

The following Examples further illustrate the present invention. Parts and 
percentages, shown therein are by weight unless otherwise stated. 
EXAMPLE 1 
Diethyl 1,3,3-trimethyl-5-oxocyclohexanephosphonate (B.Pt. 
128.degree.-30.degree./0.6 mm) was prepared by base catalysed addition of 
diethyl phosphite to isophorone. Hydrolysis of this ester with c.HCl gave 
1,3,3-trimethyl-5-oxocyclohexanephosphonic acid (M.Pt. 
167.degree.-8.degree. C.). 
22 parts of 1,3,3-trimethyl-5-oxocyclohexanephosphonic acid were added 
portion wise, over 6 hours, to a stirred solution of 0.05 parts of 
ammonium metavanadate in 32 parts of 70% nitric acid at 
55.degree.-60.degree. C.; when the addition was complete the resulting 
solution was heated at 55.degree.-60.degree. C. for a further 5 hours, 
cooled to room temperature, and diluted by the addition of 50 parts of 
water. This solution was evaporated to dryness, the solid residue 
redissolved in 100 parts of water and again evaporated to dryness to give 
21.7 parts of a hygroscopic solid which was substantially a 1:1 mixture of 
2,4,4-trimethyl-2-phosphonoadipic acid and 
3,5,5-trimethyl-3-phosphonoadipic acid which had .sup.31 P chemical shifts 
of -25 and -32 ppm respectively and a minor proportion of 
2,4,4-trimethyl-2-phosphono glutaric acid having a .sup.31 P chemical 
shift of -24 ppm. 
EXAMPLE 2 
Diethyl 1-methyl-5-oxocyclohexanephosphonate (B.Pt. 
130.degree.-2.degree./0.8 mm) was prepared by the base catalysed addition 
of diethylphosphite to 3-methyl-2-cyclohexen-1-one. Hydrolysis of this 
ester with concentrated HCl gave 1-methyl-5-oxocyclohexanephosphonic acid 
as a viscous oil. 
Oxidation of 19.2 parts of the phosphonic acid with 70% nitric acid, as in 
Example 1, gave 20.7 parts of an hygroscopic solid which was substantially 
a 1:1 mixture of 2-methyl-2-phosphonoadipic acid and 
3-methyl-3-phosphonoadipic acid which had .sup.31 P chemical shifts of -24 
ppm and -32 ppm respectively. 
EXAMPLE 3 
Diethyl 1,3-dimethyl-5-oxocyclohexanephosphonate (B.pt. 120.degree./0.1 mm) 
was prepared by the base catalysed addition of diethylphosphite to 
3,5-dimethyl-2-cyclohexen-1-one. Hydrolysis of the ester in concentrated 
HCl gave 1,3-dimethyl-5-oxocyclohexanephosphonic acid as a viscous oil. 
Oxidation of 18.7 parts of the phosphonic acid with 70% nitric acid, as in 
Example 1, gave 17.6 parts of an hygroscopic solid which was substantially 
a 1:1 mixture of 2,4-dimethyl-2-phosphonoadipic acid and 
3,5-dimethyl-3-phosphonoadipic acid, having .sup.31 P chemical shifts of 
-25 ppm and -31 ppm respectively. 
EXAMPLE 4 
A concentrated aqueous solution of the mixed product from Example 1 was 
allowed to stand at room temperature for several days during which time a 
white solid precipitated. This was collected by filtration and dried to 
give 3,5,5-trimethyl-3-phosphonoadipic acid (m.pt. 167.degree.-8.degree. 
C., decomposing, .sup.31 P chemical shift of -32 ppm) which had the 
following elemental analysis by weight. 
______________________________________ 
C H P 
______________________________________ 
Required for C.sub.9 H.sub.17 O.sub.7 P . 11/2H.sub.2 O 
36.61 6.78 10.50% 
Found 36.71 6.66 10.43% 
______________________________________ 
EXAMPLE 5 
Diethyl 5-oxocyclohexanephosphonate (B.Pt. 142.degree.-3.degree. C./0.2 mm) 
was prepared by the base catalysed addition of diethylphosphite to 
2-cyclohexen-1-one. 
Oxidation of 23.3 parts of the phosphonic ester with 70% nitric acid as in 
Example 1, followed by hydrolysis with concentrated hydrochloric acid gave 
22.6 parts of a viscous oil which was substantially a 1:1 mixture of 
2-phosphonoadipic acid and 3-phosphonoadipic acid, having .sup.31 P 
chemical shifts of -20 ppm and -30 ppm respectively. 
EXAMPLE 6 
Ethyl 4-bromocrotonate (19.3 parts) was added dropwise at 
25.degree.-30.degree. C. to a solution of the sodium salt of ethyl 
2-diethylphosphonopropionate, prepared from 23.8 parts of ethyl 
2-diethylphosphonopropionate and 5.3 parts of sodium hydride (50% in oil) 
in dioxan. The resulting solution was heated at reflux for 18 hr., after 
which time the sodium bromide was removed by filtration and the solution 
concentrated in vacuo. The residual oil was distilled to give 12.7 parts 
of ethyl 5-carboethoxy-2-diethylphosphono-2-methylpent-4-enoate boiling at 
158.degree./0.2 mm. Hydrogenation of 12 parts of this material over 5% 
palladium on carbon gave 7.2 parts of diethyl 
2-diethylphosphono-2-methyladipate boiling at 146.degree.-52.degree. 
C./0.05 mm; subsequent hydrolysis of 5 parts of this in concentrated 
hydrochloric acid gave 3.7 parts of 2-methyl-2-phosphonoadipic acid as a 
glassy solid which had a .sup.31 P chemical shift of -24 ppm. 
EXAMPLE 7 
Ethyl 5-carbomethoxy-2-diethylphosphono-4-methylpent-4-enoate (boiling at 
160.degree. C./0.3 mm) was prepared by reaction of methyl 
4-bromo-3-methylcrotonate with the anion of triethylphosphonoacetate in 
dioxan as in Example 6. 
Hydrogenation over 10% palladium on carbon gave ethyl 
5-carbomethoxy-2-diethylphosphono-4-methylpentanoate, boiling at 
166.degree. C./0.2 mm (Found: P, 8.96%; C.sub.14 H.sub.26 O.sub.7 P 
required: P, 9.18%). Hydrolysis of 10 parts of this material with 
concentrated hydrochloric acid gave 8.3 parts of 
4-methyl-2-phosphonoadipic acid as a glassy solid having a .sup.31 P 
chemical shift of -20 ppm and the following elemental analysis by weight. 
Found: C, 34.94%; H, 5.99%. PG,19 
C.sub.7 H.sub.13 O.sub.7 P requires: C, 35.01%; H, 5.46%. 
EXAMPLE 8 
Ethyl 5-carbomethoxy-2-diethylphosphono-2,4-dimethylpent-4-enoate (boiling 
at 160.degree.-4.degree. C./0.2 mm) was prepared by the reaction of methyl 
4-bromo-3-methylcrotonate with the anion of ethyl 
2-diethylphosphonopropionate in dioxan as in Example 6. Hydrogenation over 
platinum dioxide gave ethyl 
5-carbomethoxy-2-diethylphosphono-2,4-dimethylpentanoate, boiling at 
146.degree. C./0.1 mm. Subsequent hydrolysis with concentrated 
hydrochloric acid gave 2,4-dimethyl-2-phosphonoadipic acid as a glassy 
solid, having a .sup.31 P chemical shift of -25 ppm and the following 
elemental analysis by weight: 
Found: C, 35.01%, H, 5.82%; P, 11.00%. 
C.sub.8 H.sub.15 O.sub.7 P.H.sub.2 O requires: C, 35.29%; H, 6.25%; P, 
11.39%. 
EXAMPLE 9 
A solution of titanium tetrachloride (7.7 parts by vol.) in dry carbon 
tetrachloride (18 parts by vol.) was added dropwise at 0.degree. C. to dry 
tetrahydrofuran (140 parts by vol.). To this solution at 0.degree. C. was 
added dropwise a mixture of triethylphosphonoacetate (7.9 parts) and ethyl 
3-formyl-3-methylbutyrate (5.6 parts) (prepared by the method of G. Opitz 
et al., Ann. 1961, 649, 36) followed by addition of a solution of 
N-methylmorpholine (15.4 parts by vol.) in dry tetrahydrofuran (26 parts 
by vol.) over 30 min. The resulting mixture was stirred at 0.degree. C. 
for 22 hr., water (50 parts by vol.) was added, and stirred at 
20.degree.-25.degree. C. for 30 min. This was then ether extracted 
(4.times.50 parts by vol.) and the bulked ether extracts washed with water 
(2.times.25 parts by vol.) and dried over magnesium sulphate. The ether 
was removed by evaporation and the residual oil distilled to give 7.2 
parts of ethyl 
5-carboethoxy-2-diethylphosphono-4,4-dimethyl-pent-2-enoate, boiling at 
142.degree.-4.degree. C./0.1 mm, as a cis-trans mixture. 
Hydrogenation of this (10.2 parts) over platinum dioxide catalyst gave 
diethyl 2-diethylphosphono-4,4-dimethyladipate boiling at 
144.degree.-6.degree. C./0.1 mm having a .sup.31 P chemical shift of -23 
ppm. Hydrolysis of this ester in concentrated hydrochloric acid gave 
4,4-dimethyl-2-phosphonoadipic acid as a glassy solid having a .sup.31 P 
chemical shift of -21 ppm. 
EXAMPLE 10 
Diethyl 2-diethylphosphono-4,4-dimethyladipate (3.6 parts) (See Example 9) 
was added dropwise to a suspension of sodium hydride (0.6 parts, 50% in 
oil) in dry dioxan (100 parts by volume) containing methyliodide (14.2 
parts) over 2 hr. at room temperature. The resulting solution was stirred 
at room temperature for 18 hr. then heated to reflux for 2 hr., cooled, 
the solids removed by filtration and the filtrate concentrated in vacuo. 
Distillation of the residual oil gave 3 parts of diethyl 
2-diethylphosphono-2,4,4-trimethyladipate, boiling at 
137.degree.-8.degree. C./0.03 mm having a .sup.31 P chemical shift of -26 
ppm and having the following elemental analysis by weight. 
Found: C, 53.57; H, 8.91; P, 7.85%. 
C.sub.17 H.sub.33 O.sub.7 P requires: C, 53,67; H, 8.74; P, 8.14%. 
Hydrolysis of this ester in concentrated hydrobromic acid gave 
2,4,4-trimethyl-2-phosphonoadipic acid as a hygroscopic solid having a 
.sup.31 P chemical shift of -25 ppm. 
EXAMPLE 11 
Demonstration of Corrosion Inhibitor Activity of Product of Example 1 
Corrosion inhibitor activity of the product of Example 1 was demonstrated 
in the following way by the Aerated Solution Bottle Test and using a 
standard corrosive water made up as follows: 
20 g CaSO.sub.4 2H.sub.2 O 
15 g MgSO.sub.4 7H.sub.2 O 
4.6 g NaHCO.sub.3 
7.7 g CaCl.sub.2 6H.sub.2 O 
45 gallons distilled water 
Mild steel coupons, 5 cms.times.2.5 cms are scrubbed with pumice immersed 
for one minute in hydrochloric acid and then rinsed, dried and weighed. 
The desired proportion of additive combination is dissolved in 100 ml of 
standard corrosive water. A steel coupon is suspended in the solution, and 
the whole is stored in a bottle in a thermostat at 40.degree. C. During 
the storage period, air is passed into the solution at 500 ml/minute, the 
passage of the air being screened from the steel coupon; any water losses 
by evaporation are replaced as they occur with distilled water from a 
constant head apparatus. 
After 48 hours, the steel coupon is removed, scrubbed with pumice, immersed 
for one minute in hydrochloric acid inhibited with 1% by weight of 
hexamine and then rinsed, dried and reweighed. A certain loss in weight 
will have occurred. 
A blank test i.e. immersion of a mild steel specimen in the test water in 
the absence of any potential corrosion inhibitor, is carried out with each 
series of tests. The corrosion rates are calculated in milligrams of 
weight loss/sq. decimeter/day (m.d.d) but for convenience the results are 
shown as percentage protection, which is defined as follows: 
##EQU1## 
The results obtained using 100 parts per million of the product of Examples 
1, 2 and 4 are given in Table I. 
TABLE I 
______________________________________ 
Product (100 ppm) 
% Protection 
______________________________________ 
Product of Example 1 
92 
Product of Example 2 
93 
Product of Example 4 
86 
______________________________________ 
EXAMPLE 12 
Demonstration of dispersant activity for iron oxide 
To carry out this test a sample of iron oxide is prepared as follows: 
An excess of 0.88 ammonium hydroxide solution is added to 500 milliliters 
of a 20% weight/volume solution of FeSO.sub.4.7H.sub.2 O with vigorous 
stirring. The solution is brought to the boil and filtered under reduced 
pressure through a Whatman No. 54 filter paper. The filtered precipitate 
is washed with hot water several times and then sucked dry. The filter 
cake is dried in an oven at 105.degree. C. for 2 to 3 hours on a watch 
glass, then ground in a mortar and pestle to a fine powdery consistency. 
0.20 grams of this iron oxide are weighed out into a 100 milliliter 
measuring cylinder, distilled water added up to the 80 milliliter level 
and the cylinder placed in a water bath at 50.degree. C. When the solution 
has equilibrated at 50.degree. C., 20 milliliters of a solution containing 
the additive is added and the suspension stirred thoroughly with a glass 
rod. The cylinder is allowed to stand a further 2 minutes, then removed 
from the water bath and the contents allowed to settle. After 20 minutes 
the optical density of the suspension is measured at 500 nm in a 1 
centimeter cell. In the absence of additive the optical density was 0.35 
and in the presence of the product of Example 1, at weight ratio of 1 part 
product of Example 1: 20 part iron oxide, the optical density was 0.78. 
This demonstrates the ability of the product of Example 1 to keep iron 
oxide in suspension. 
EXAMPLES 13 and 14 
Evaluation of scale inhibiting activity 
The compounds were evaluated as scale inhibitors in a recirculating water 
evaporative cooling test ring simulating the major features of an 
industrial cooling system. 
The rig comprises an electrically heated heat exchanger, cooling tower, 
tower sump, reservoir, and make up and blowdown facilities. Feed water to 
the rig had the following analysis: 
______________________________________ 
pH PA TA TH Cl.sup.- 
______________________________________ 
7.39 nil 125 157 37 
______________________________________ 
In the analytical data, the signification of the abbreviations used is as 
follows: 
PA is phenol alkalinity (ppm of CaCO.sub.3) 
TA is total alkalinity (ppm of CACO.sub.3) 
TH is total hardness (ppm of CACO.sub.3) 
The operating parameters for the results described were: 
Recirculation rate: 106 gallons per hour 
Water Velocity: 1.4 feet per second 
Maximum water temperature: 46.degree. C. 
Temperature rise through heater: 3.degree. C. 
Evaporation Rate: 1.8 liters per hour 
Concentration factor: 3.0 
The quantity of compound under test necessary to give the required dose 
level is added to 200 liters of feed water in the make up tank. The rig is 
then filled (20 liters capacity) and run until the required concentration 
factor has been reached. Constant volume is maintained in the system by 
means of an automatic level control. The heat exchanger is then stripped 
down and the weight of scale deposited determined. After cleaning and 
reassembling the heat exchanger, the rig is restarted with the blowdown 
pump switched on and set to maintain the system at a concentration factor 
of 3. The rig is then operated until 100 liters of feed water have been 
used. The weight of scale deposited on the heat exchanger is then 
determined. Two weights of scale are thus obtained for each test, one 
whilst the rig is being concentrated and the second after a period of 
operation at the desired concentration factor. The results are expressed 
as a scaling rate, that is, milligrams of scale deposited per liter of 
feed water added. 
The scale deposited in these tests consists mainly of calcium carbonate and 
the results are given in Table II. 
______________________________________ 
Scaling rate milligrams/ 
Dose to feed 
liter 
Example 
Additive ppm solids Concentration 
Run 
______________________________________ 
Nil Nil 32.8 35.1 
Proudct 5 1.5 5.7 
13 of Ex- 2.5 8.4 7.5 
ample 1 
Product 10 2.4 2.4 
14 of Ex- 5 1.8 3.4 
ample 4 2.5 8.9 2.3 
______________________________________