GB2077259A

GB2077259A - Methacrylic Acid and its Esters

Info

Publication number: GB2077259A
Application number: GB8116437A
Authority: GB
Original assignee: Davy Mckee Oil and Chemicals Ltd
Current assignee: Johnson Matthey Davy Technologies Ltd
Priority date: 1980-06-06
Filing date: 1981-05-29
Publication date: 1981-12-16

Abstract

Methacrylic acid and its esters are produced by oxidising a t-alkyl or cycloalkyl ether of 2-methyl-3- hydroxypropionaldehyde, such as 3-t- butoxy-2-methyl-propionaldehyde possibly followed by an esterification step, and the resulting acid or ester is then subjected to deetherification and dehydration. Olefin, e.g. iso-butylene, released upon deetherification can be reacted with allyl alcohol to form the corresponding allyl t-alkyl or -cycloalkyl ether which can then be hydroformylated to give the t-alkyl or -cycloalkyl ether of 2-methyl-3- hydroxypropionaldehyde, thus permitting operation of a cyclic process.

Description

SPECIFICATION Production of Methacrylic Acid and its Esters This invention relates to the production of methacrylic acid and of its esters.

According to the present invention there is provided a process for the production of a compound of the general formula: CH2=C(CH3)-COOR' (I) wherein R' represents a hydrogen atom or an optionally substituted hydrocarbon radical, which comprises converting an aldehyde-ether of the general formula

wherein R1 and R2 each, independently of the other represent a C1 to C4 alkyl radical, and R3 and R4 each, independently of the other, represent a hydrogen atom or a C1 to C3 alkyl radical, or wherein R1 represents a C1 to C4 alkyl radical, R2 and R3 together with the carbon atoms to which they are attached form a 5-membered or 6-membered cycloaliphatic ring, and R4 represents a hydrogen atom or a C1 to C3 alkyl radical, to a compound of the general formula::

wherein R', R1, R2, R3 and R4 are as defined above, followed by deetherification and dehydration.

Preferably R1 and R2 each, independently of the other, represents a methyl or ethyl group and R3 and R4 each, independently of the other, represents a hydrogen atom or a methyl group.

In a particularly preferred process the compound of formula (II) is: (CH3)3C-0-CH2-CH(CH3)-CH0 The radical R' may be a substituted hydrocarbon radical which preferably contains from 1 to about 30 carbon atoms. Preferably R' represents a hydrogen atom or an optionally substituted alkyl radical containing, for example, from 1 to about 25 carbon atoms. Alternatively R' may represent a cycloaliphatic radical, such as cyclopentyl, 1 '-methyl-cyclopentyl, cyclohexyl, 1 '-methylcyclohexyl, or the like, or an aromatic radical, such as phenyl, p-methoxyphenyl, naphthyl-1 or -2, or the like.When R' is a substituted hydrocarbon radical typical substituents may include one or more groups selected from chlorine, bromine, hydroxy, nitro, alkoxy, dialkylamino, phenoxy, alkoxycarbonyl, alkylcarbonyloxy, alkylsulphonyloxy, arylsulphonyloxy, and the like. Preferred meanings for R' are hydrogen, methyl, ethyl, n-butyl, iso-buty, n-hexyl, 2-ethylhexyl, lauryl, tridecyl, stearyl, 2-diethylaminoethyl, 2diisopropylaminoethyl, and the like.Thus typical compounds of the formula (I) include: methacrylic acid; methyl methacrylate; ethyl methacrylate; n-butyl methacrylate; iso-butyl methacrylate; n-hexyl methacrylate; 2-ethylhexyl methacrylate; 2-hydroxyethyl methacrylate; 2-hydroxypropyl methacrylate; lauryl methacrylate; tridecyl methacrylate; stearyl methacrylate; higher alkyl methacrylate derived from commercially available mixtures of higher aliphatic alcohols, e.g. C12-C14 alcohol mixtures, C18C18 alcohol mixtures, C18-C20 alcohol mixtures and the like; 2-diethylaminoethyl methacrylate; and 2-diisopropylaminoethyl methacrylate.

The compounds of formula (II) can be made by hydroformylation of an allyl t-alkyl or-cycloalkyl ether of the general formula:

wherein, R1, R2, R3 and R4 are as defined above. In this reaction the allyl ether of formula (IV) is contacted with hydrogen and carbon monoxide under hydroformylation conditions in the presence of a catalytic amount of a hydroformylation catalyst. The catalyst may be any Group VIII metal-containing catalyst known to be suitable for catalysing the hydroformylation of terminal olefins. The hydroformylation conditions are selected so as to be suitable for the chosen catalyst. Further details of the production of the compounds of formula (I!) can be found in European patent application No.

80301129.5 the disclosure of which is herein incorporated by reference.

The allyl ethers of formula (IV) can be prepared in known manner by reaction of allyl alcohol in the presence of an acidic catalyst with an olefin of the general formula:

wherein R1, R2, R3 and R4 are as defined above. As examples of olefins of the formula (V) there can be mentioned iso-butylene, 2-methylbut-1 -ene, 2-methylbut-2-ene, 2,3-dimethylbut-2-ene, 3methylpent-2-ene, 2-ethylbut-1 -ene, 1 -methyl-cyclohexene and 1 -methylcyclopentene.

Etherification of allyl alcohol can be effected by reaction with an olefin of the general formula (V), conveniently in the presence of an acidic catalyst. The etherification is a reversible reaction and is favoured by the use of low temperatures, for example a temperature in the range of from about OOC to about 800 C. Usually it will be preferred to effect etherification of alkyl alcohol at about 600C or less, preferably in the range of from about 1 50C to about 600 C for example in the range of from about 35 OC to about 600C. Since the olefin may be volatile it may be necessary to effect the etherification reaction under elevated pressure.Typical acidic catalysts include ion exchange resins, preferably in anhydrous form, containing sulphonic acid and/or carboxylic acid groups, such as Amberlyst 1 5 and Dowex (Registered Trade Mark) 50 resins, as well as aqueous acids, e.g. aqueous solutions of phosphoric acid or dilute aqueous solutions of sulphuric acid (containing, for example, 10% w/v sulphuric acid or less), acid zeolites, acid clays, and organic acids such as p-toluenesulphonic acid or formic acid.

The step of converting a compound of the general formula (II) to a compound of the general formula (III) involves an oxidation step followed, if R' does not represent a hydrogen atom, by an esterification step.

Deetherification of the compounds of formula (II) is conveniently accomplished by treatment with an acidic catalyst, e.g. with an aqueous acid, an acidic ion exchange resin, an acidic clay, an acidic alumina, an acidic alumino-silicate, or silica. Deetherification and dehydration can be carried out stepwise but are preferably effected simultaneously. Hence deetherification is preferably effected under dehydrating conditions. Such conditions may include use of elevated temperatures, for example temperatures in excess of about 600 C, e.g. about 800C up to about 1 200C or more. Usually it will be preferred to use a temperature of not more than about 2500C in the deetherification step.

Deetherification can be carried out in the presence, but preferably in the absence, of an added inert solvent In this step the olefin of the general formula (V) is regenerated. Hence, according to a particularly preferred process a compound of the general formula (I) is prepared by the steps comprising: : (a) reacting allyl alcohol with an olefin of the general formula (V) in the presence of an acidic catalyst to form an allyl ether of the general formula (IV); (b) contacting resulting allyl ether of the general formula (IV) with hydrogen and carbon monoxide under hydroformylation conditions in the presence of a catalytic amount of a hydroformylation catalyst; (c) converting resulting aldehyde-ether of the general formula (II) to a compound of the general formula (Ill); (d) subjecting resulting compound of the general formula (III) to deetherification and dehydration conditions; (e) recovering resulting compound of the general formula (I) and regenerated olefin of the general formula (V); and (f) recyling resulting regenerated olefin of the formula (V) to step (a).

Recovery of the compound of the general formula (I) can be effected in any convenient manner.

For example, if deetherification has been effected by contact with an acidic ion exchange resin, the product acid or ester can be recovered by distillation. On the other hand when using an aqueous acid for deetherification, the organic layer containing the product acid or ester and possibly also unreacted tertiary ether material and/or solvent (if present) may be dried and distilled.

In the deetherification of the compounds of formula (III) there may be formed as by-product a tertiary alcohol of the general formula:

wherein R,, R2, R3 and R4 are as defined above. Such an alcohol of the general formula (VI) may be dehydrated in the presence of an acidic catalyst, such as one of those mentioned above for use in the deetherification step, to form a corresponding olefin of the general formula (V) which can be recycled for reaction with allyl alcohol in step (a).

Oxidation of the aldehyde-ether of the general formula (II) can be accomplished using any suitable mild oxidising agent. Amongst oxidising agents that can be used for oxidation of aldehyde groups to carboxylic acid groups there can be mentioned alkaline permanganate solutions (e.g. alkaline KM nO4 solutions). Alternatively gaseous oxygen, whether in the form of pure oxygen, oxygen-enriched air or air can be used as oxidising medium, optionally in the presence of a catalyst suitable for catalysing the oxidation of aldehydes to acids.Examples of catalysts suitable for catalysing oxidation of aldehydes to acids using gaseous oxygen include vanadyl sulphate, manganous acetate, cobalt acetate (e.g. manganous acetate or cobalt acetate in acetic acid), as well as noble metal catalysts such as palladium on charcoal, platinum on charcoal or a hydroformylation catalyst, particularly a rhodium hydroformylation catalyst, or catalyst precursor, for example RhH(CO)(PPH3)3.

When R' is not hydrogen, production of the compound of the general formula (I) requires an esterification step. This can be effected in known manner either simultaneously with or subsequent to oxidation of the compound of the general formula (II) to form the acid of the general formula:

wherein R,, R2, R3 and R4 are as defined above. Thus, for example esterification can be effected by reaction of the acid of the general formula (VII) with the corresponding alcohol of the formula R'OH in the presence of an acidic or basic catalyst. Alternatively esterification can be effected by reaction of an ester of the general formula R"COOR', wherein R" is a hydrocarbon radical, such as methyl or butyl, with the acid of the general formula (VII) in the presence of a suitable transesterification catalyst, e.g.

an acidic or basic catalyst. Typical acidic catalysts include acids such as sulphuric acid, ptoluenesulphonic acid, formic acid, phosphoric acid, acidic ion exchange resins containingCOOH or -SO3H groups, acid clays, silica, acid zeolites and the like. Amongst suitable basic catalysts there can be mentioned sodium hydroxide, potassium hydroxide and the like. Typical esterification conditions include the use of elevated temperatures and, optionally, the use of elevated pressures. Thus esterification may be effected at temperatures of about 500C or more, e.g. up to about 2500C.

As examples of alcohols of the formula R'OH to be used in esterification there can be mentioned: methanol, ethanol, n-butanol, iso-butanol, n-hexanol, 2-ethylhexanol, ethylene glycol, 1 2-propylene glycol, lauryl alcohol, tridecyl alcohol, stearyl alcohol, commercially available mixtures of higher aliphatic alcohols (e.g. C12-C14 alcohol mixtures, C16-C18 alcohol mixtures, and C -C20 alcohol mixtures), 2-diethylaminoethanol, 2-diisopropylaminoethanol, and the like.

In the hydroformylation step, the hydroformylation catalyst may be any Group VIII metalcontaining hydroformylation catalyst known to be effective for catalysing the hydroformylation of terminal olefins. Preferably the catalyst is a rhodium-containing catalyst comprising rhodium in complex combination with carbon monoxide and a triorganophosphine ligand, such as triphenylphosphine. When using such a catalyst the concentration of rhodium in the reaction medium may range from about 5 parts per million by weight up to about 1000 parts per million of rhodium or more, calculated as rhodium metal. Typically the rhodium concentration ranges from about 20 parts per million up to about 400 parts per million, e.g. about 40 to about 300 parts per million, calculated as rhodium metal.The reaction medium may contain excess triorganophosphine, e.g. about 2 moles up to about 1000 moles or more of excess free triorganophosphine per gram atom of rhodium. Usually the hydrogen:carbon monoxide molar ratio is approximately 1 :1, e.g. about 1.05:1. The hydroformylation conditions typically include use of reaction temperatures of from about 200C up to about 1 600C, e.g. about 700C to about 1 200C and use of a partial pressure of hydrogen of from about 0.1 kg/cm2 absolute up to about 10 kg/cm2 absolute or more and a partial pressure of carbon monoxide of about 0.1 kg/cm2 absolute up to about 10 kg/cm2 absolute or more. The overall pressure may be about 20 kg/cm2 or less.The reaction can be effected in the presence of a solvent, e.g. a mixture of aldehyde condensation products such as is disclosed in British Patent Specification No.

1,338,237, or in the absence of added solvent.

The invention is further illustrated by reference to the following Examples.

Example 1 A. Preparation of allyl t-butyl ether 50 ml allyl alcohol and 5 g dry Amberlyst 1 5 resin were placed in a 300 ml capacity autoclave agitated by means of a Magnedrive unit actuating an induction stirrer. (The word "Amberlyst" is a Registered Trade Mark). The autoclave was purged with iso-butylene and then warmed to 300C in an oil bath and pressurised to 1.75 kg/cm2 absolute with iso-butylene. The pressure dropped as reaction took place and furtheriso-butylene was introduced to raise the pressure once again to 1.75 kg/cm2.

This procedure was repeated as necessary until reaction was complete after approximately 90 minutes as indicated by the cessation of uptake of iso-butylene. After releasing the pressure the product was decanted from the resin and washed several times with deionised water. The crude product was subjected to a partial vacuum to remove iso-butylene (until gas chromatography showed that there was less than 0.1% iso-butylene in the product) and then dried over anhydrous sodium carbonate. Gas chromatography, using a gas chromatograph with a flame ionisation detector and temperature programming, indicated that allyl t-butyl ether had been formed with greater than 98% efficiency. The chromatographic column was 1.83mx3.2mm O.D. stainless, steel, packed with 10% by weight diethylene glycol succinate on Chromosorb W.

B. Hydroformylation of allyl-t-butyl ether 0.10 gms rhodium hydridocarbonyl tris(triphenylphosphine), i.e. RhH (CO) (PPh3)3, 90 ml ally tbutyl ether and 10.0 gms triphenylphosphine were charged to a 300 ml autoclave fitted with a magnetically coupled stirrer, a gas inlet dip tube and an outlet valve. The autoclave was sealed, purged with nitrogen whilst stirring its contents, and isolated. Stirring was continued whilst the temperature of the autoclave was raised to 730C by immersion in an oil-bath fitted with a thermostatically-controlled heater-stirrer. The autoclave was then purged with a 1:1 molar H2:CO mixture and pressurised to 2.1 kg/cm2 absolute by closure of the outlet valve. Reaction commenced and proceeded smoothly with a slight exotherm at the beginning of the reaction.As the reaction proceeded, the pressure dropped; when the total pressure reached 1.9 kg/cm2 absolute, more 1:1 H2:CO mixture was admitted to the autoclave to restore the pressure to 2.1 kg/cm2 absolute. This repressurisation technique was repeated as necessary until no more gas was taken up, indicating that reaction was complete. This took between 3 and 4 hours. The autoclave was cooled, depressurised and opened, and the contents discharged and stored under nitrogen.

The resulting solution was analysed by gas chromatography using helium as carrier gas, a column packed with 10% w/w diethylene glycol succinate on Chromosorb PAW and a flame ionization detector. Selectivities were observed as follows:- 5.6% to isomerised/hydrogenated allylic feedstock 18.9% to 3-t-butoxy-2-methyl propionaldehyde (TBMPA) 75.5% to 4-t-butoxybutyraldehyde (TBBA).

These selectivities are expressed in molar percentages.

The two aldehyde-ethers (TBMPA and TBBA) were separated by distillation from the other constituents of the reaction solution and then purified by distillation and characterised by formation of dimedone derivatives and by measurement of physical data. The following results were obtained Property TBMPA TBBA Refractive index 1.4128 1.4170 (at 230C) Melting point of 107-1 090C 133-1 350C dimedone derivative Specific gravity at 0.849 0.868 25CC Boiling point at 743 mm Hg 151.60C 169.50C at 760 mm Hg 152.30C 170.50C at 100 mm Hg 1 03.20C 11 5.60C Nuclear magnetic resonance spectra were obtained for the compounds as follows, using tetramethyl silane as an internal standard and carbon tetrachloride as solvent: 1.TBBA (CH3)3C-O-CH2-CH2-CH2-CHO a b c d e Identifying letter of C-atom to which Chemical shift H-atom is attached Nature of peak 8 relative to TMS a singlet 1.13 b triplet 3.31 c triplet of triplets 2.39 d doublet of triplets 1.84 e triplet 9.62 2. TBMPA (CH3)3C-O-CH2-CH (CH3)-CHO a b cd e Identifying letter of C-atom to which Chemical shift H-atom is attached Nature ofpeak 8 relative to TMS a singlet 1.16 b doublet 3.56 c complex multiplet 2.39 d doublet 1.04 e doublet 9.66 In each case the ratios of the peak areas corresponded to the expected ratios as predicted from the respective assigned structural formula.In the case of the doublets, triplets and multiplets the quoted chemical shift is the centred value.

C. Oxidation of 3-t-butoxy-2-methyl-propionaldehyde 10 gms 62% w/w pure 3-t-butoxy-2-methylpropionaldehyde were charged to a 50 ml roundbottomed flask and heated to 700C under an atmosphere of oxygen by means of an oil bath, whilst stirring by means of a magnetic stirrer and follower. (The balance of the starting material was essentially 4-t-butoxy-butyraldehyde). Heating and stirring were continued overnight, whereupon the resulting solution was cooled and analysed by gas chromatography. Utilising the same gas chromatography technique as described above in Part B of this Example, the product was shown to contain 5.30 gms of a new compound, corresponding to a yield of 76.9%. The structure 3-t-butoxy-2methyl-propionic acid was assigned to this compound.Proof of this structure was provided by the production of methyl methacrylate therefrom, as described in Part D below.

D. Production of Methyl Methacrylate 1.79 gms of the product from Part C of this Example, 10 ml concentrated phosphoric acid and 10 ml methanol were charged to a 50 ml flask fitted with a reflux condenser and provided with a side arm fitted with a septum. This mixture was heated in an oil bath at 800C for 1 hour under reflux whilst stirring by means of a magnetic stirrer and follower. The flask was then cooled to 300C and the condenser re-arranged for distillation. The oil bath temperature was then raised to 2000C. As the reactants and products flashed from the reaction vessel 5 ml methanol were slowly introduced by means of a syringe through the septum. 1 6 ml condensate were collected in the receiver and analysed by the gas chromatographic technique described above in Part B of this Example.This analysis showed that 0.415 gm methyl methacrylate had been produced, corresponding to a yield of 77.7%. The identity of this product as methyl methacrylate was confirmed by use of an authentic sample of this material under the conditions used for the gas chromatographic analysis. Other compounds identified in the condensate were methanol and methyl t-butyl ether.

Example 2 Production of Methacrylic Acid 30 ml concentrated phosphoric acid were put in a 50 ml flask fitted for distillation and having a side arm fitted with a septum and were heated in an oil bath at 2000C whilst stirring using a magnetic stirrer and follower.8.07 gms of the product from Part C of Example 1 were then added slowly through the septum to the hot stirred phosphoric acid by means of a syringe. The products flashed from the reaction flask, and were condensed and collected in a receiver. 6.6 ml condensate were collected.

Analysis by the gas chromatographic technique described in Part B of Example 1 indicated that the condensate contained 0.67 gms methacrylic acid, the identity of which was proved by comparison with an authentic sample. This corresponds to a yield of 32.3%.

Example 3 The procedures of Parts C and D of Example 1 are repeated using air at atmospheric pressure, in place of pure oxygen as the oxidising medium in Part C, with equally good results.

Example4 When the procedure of Part A of Example 1 is repeated, using in place of iso-butylene, an equivalent amount of 2-methylbut-2-ene, 2,3-dimethylbut-2-ene or 1 -methylcyclohexene, there is obtained allyl 2-methylbut-2-yl ether, allyl 2,3-dimethylbut-2-yl ether, and allyl 1-methylcyclohexyl ether respectively. Each of these compounds is used, in place of allyl t-butyl ether, in the procedure of Examples 1 and 2 with similar results.

Example 5 A. Oxidation of 3-t Butoxy-2-Methyl-Propionaldehyde 80.0 gm of 91.3% wt/wt pure 3-t-butoxy-2-methyl-propionaldehyde and 0.07 gm manganous acetate (CH3COO)2 Mn.4H2O were charged to a 300 ml autoclave fitted with a magnetically coupled stirrer, cooling coii, thermocouple, a gas inlet dip tube and an outlet gas valve. The autoclave was sealed, purged with oxygen whilst stirring its contents, the exit valve isolated and the pressure raised to and controlled at 300 psia (21.09 kg/cm2 absolute) by means of a pressure controller.

The temperature of the autoclave was raised to 500C by immersion in an oil bath fitted with a thermostatically controlled heater stirrer. Oxygen consumption was noticeable even at room temperature utilising an in-line fiow meter, the flow rate increasing with increasing temperature.

When the temperature reached 500C the exothermic reaction was controlled by means of water cooling through the coil immersed in the solution, the water supply being activated by means of a thermostatically controlled solenoid valve.

The reaction proceeded vigorously as denoted by the oxygen consumption and when this ceased, the reaction was deemed to be complete. This took 121 hours. The autoclave was cooled, depressurised and opened and the contents (85.5 gm) discharged and stored under nitrogen.

The resultant solution was analysed by gas chromatography using helium as carrier gas, a column packed with 10% w/w diethylene glycol succinate on Chromosorb (Registered Trade Mark) PAW and a flame ionisation detector.

The product was shown to contain 68.9% 3-t-butoxy-2-methyl-propionic acid, corresponding to a yield of 76.0%.

B. Production of Methacrylic Acid 30 gm of a solution containing 68.9% wt/wt pure 3-t-butoxy-2-methyl-propionic acid, 3 gm silica alumina catalyst (30--60 mesh) and 0.1 gm hydroquinone were charged to a 75 ml round bottomed flask fitted with a lagged air condenser with thermometer and side arm leading to a water cooled condenser and receiver.

The mixture was heated in an oil bath at 2000C for four hours. As the reaction proceeded, the temperature at the top of the condenser rose to 1 C before collapsing as the reaction terminated.

/so-butylene was evolved during the time the reaction was proceeding. At the termination of the test the oil bath was lowered and the flask allowed to cool. Subsequently the condenser was washed through to the receiver and the solution made up to 50 ml with methanol.

This solution was analysed by gas chromatography using helium as carrier gas, a column packed with 10% wt/wt di-ethylene glycol succinate on Chromosorb PAW and a flame ionisation detector. The sample was found to contain 15.6% wt/vol methacrylic acid, corresponding to a yield of 70.2%.

Claims

1. A process for the production of a compound of the general formula: CH2=C(CH3)-COOR' (i) wherein R' represents a hydrogen atom or an optionally substituted hydrocarbon radical, which comprises converting an aldehyde-ether of the general formula

wherein R, and R2 each, independently of the other, represent a C, to C4 alkyl radical, and R3 and R4 each, independently of the other, represent a hydrogen atom or a C, to C3 alkyl radical, or wherein R, represents a C, to C4 alkyl radical, R 2 and R3 together with the carbon atoms to which they are attached form a 5-membered or 6-membered cycloaliphatic ring, and R4 represents a hydrogen atom or a C, to C3 alkyl radical, to a compound of the general formula::

2. A process according to Claim 1, in which R, and R2 each, independently of the other, represents a methyl or ethyl group and R3 and R4 each, independently ofthe other, represents a hydrogen atom or a methyl group.

3. A process according to Claim 2, in which the compound of formula (II) is: (CH3)3C-O-CH2-CH(CH3)-CHO

4. A process according to any one of Claims 1, to 3 in which the step of converting the compound of the general formula (II) to the compound of the general formula (III) comprises an oxidation step followed, if R' does not represent a hydrogen atom, by an esterification step.

5. A process according to claim 4, in which oxidation is effected by use of air, oxygen-enriched air or gaseous oxygen.

6. A process according to claim 5, in which oxidation is conducted in the absence of added catalyst.

7. A process according to claim 5, in which oxidation is conducted in the presence of a catalyst effective for catalysing oxidation of an aldehyde to an acid.

8. A process according to any one of Claims 1, to 4 in which deetherification of the compound of the general formula (II) is accomplished by treatment with an acidic catalyst selected from an aqueous acid, an acidic ion exchange resin, an acidic clay, an acidic alumina, an acidic alumino-silicate and silica.

9. A process according to any one of Claim 1 to 5 in which deetherification is conducted at a temperature in the range of from about 800C to about 2500C whereby deetherification and dehydration are effected simultaneously.

10. A process for the production of a compound of the general formula: CH2=C(CH3)-COOR' (I) wherein R' represents a hydrogen atom or an optionally substituted hydrocarbon radical, which comprises: (a) reacting allyl alcohol with an olefin of the general formula:

wherein R1 and R2 each, indepently of the other, represents a CX to C4 alkyl radical, and R3 and R4 each, independently of the other, represents a hydrogen atom or a C1 to C3 alkyl radical, or wherein R represents C1 to C4 alkyl radical R and R represents a C, to C4 alkyl radical, R2 and 3 together with the carbon atoms to which they are attached form a 5-membered or 6-membered cycloaliphatic ring, and R4 represents a hydrogen atom or a C, to C3 alkyl radical, in the presence of an acidic catalyst to form an allyl ether of the general formula:

wherein R1,R2, R and R4 are as defined above; (b) contacting resulting allyl ether of the general formula (IV) with hydrogen and carbon monoxide under hydroformylation conditions in the presence of a catalytic amount of a hydroformylation catalyst; (c) converting resulting aldehyde ether of the general formula:

wherein R1, R2, R3 and R4 are as defined above, to a compound of the general formula::

wherein R', R1, R2, R3 and R4 are as defined above; (d) subjecting resulting compound of the general formula (I II) to deetherification and dehydration conditions; (e) recovering resulting compound of the general formula (I) and regenerated olefin of the general formula (V); and (f) recycling regenerated olefin of the general formula (V) to step (a).

11. A process according to Claim 10, in which R, and R2 each, independently of the other, represents a methyl or ethyl group and R3 and R4 each, independently of the other, represents a hydrogen atom or a methyl group.

12. A process according to Claim 10 or Claim 11, in which, in the compounds of the general formulae (V), (IV), (II) and (III) R1 and R2 are each a methyl group and R3 and R4 are each a hydrogen atom.

1 3. A process according to any one of Claims 10 to 12, in which the etherification of step (a) and the deetherification of step (d) are each effected in the presence of an acidic catalyst selected from an aqueous acid, an acidic ion exchange resin, an acidic clay, an acidic alumina, an acidic alumino-silicate, and silica.

14. A process according to any one of Claims 10 to 13, in which oxidation is effected by use of air, oxygen-enriched air or gaseous oxygen.

1 5. A process according to Claim 14, in which oxidation is conducted in the absence of added catalyst.

1 6. A process according to Claim 14, in which oxidation is conducted in the presence of a catalyst effective for catalysing oxidation of an aldehyde to an acid.

1 7. A process for the production of a compound of the formula (I) set out in Claim 1 conducted substantially as herein described and exemplified.

1 8. Compounds of the general formulae (I) set out in Claim 1 whenever prepared by a process according to any one of Claims 1 to 1 7.