US3325381A - Electrolytic process for producing dihydroxycapronitrile - Google Patents

Electrolytic process for producing dihydroxycapronitrile Download PDF

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US3325381A
US3325381A US342264A US34226464A US3325381A US 3325381 A US3325381 A US 3325381A US 342264 A US342264 A US 342264A US 34226464 A US34226464 A US 34226464A US 3325381 A US3325381 A US 3325381A
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acid
dihydroxycapronitrile
monocyanhydrin
glutaraldehyde
hydrolysis
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Robert W Foreman
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Standard Oil Co
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C255/00—Carboxylic acid nitriles
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D309/00—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only ring hetero atom, not condensed with other rings
    • C07D309/02—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only ring hetero atom, not condensed with other rings having no double bonds between ring members or between ring members and non-ring members
    • C07D309/08—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only ring hetero atom, not condensed with other rings having no double bonds between ring members or between ring members and non-ring members with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D309/10—Oxygen atoms

Definitions

  • the present invention relates to a process for the production of dihydroxycapronitrile by the hydrolysis of dihydrocyanopyran to glutaraldehyde monocyanhydrin and the reduction of glutaraldehyde monocyanhydrin to dihydroxycapronitrile.
  • Step I The hydrolysis reaction may be carried out in a dilute aqueous solution of an acid, an acid salt or in the presence of a cation exchange material.
  • the acid, acid salt or cation exchange material is a catalyst and is not consumed in the reaction.
  • a dilute aqueous solution of an acid sulfate is utilized which later also may serve as the electrolyte in the electrolytic reduction step of the process.
  • Such an electrolyte can be recycled after removal of the dihydroxycapronitrile, thereby simplifying the process and reducing the consumption of acidic catalyst.
  • the electrolytic reduction of the glutaraldehyde monocyanhydrin may be conveniently carried out in an undivided cell, using preferably, a lead cathode and a lead dioxide or platinum anode. If a divider is used to separate the cathode and anode compartments, a permselective cation exchange membrane is preferred.
  • the monocyanhydrin of glutaraldehyde is fed to the cathode compartment and the product, dihydroxycapronitrile, may be recovered from the aqueous catholyte by means of solvent extraction. The electrolyte can then be recycled to the hydrolysis reaction or to the electrolytic cells as desired.
  • the hydrolysis Step I and the electrochemical reduction Step II may be conducted in separate or the same reaction vessels in a sequential or simultaneous manner and still be within the scope of the present invention. If the two steps are carried out simultaneously, however, reaction conditions must be adjusted to maximize the yields in both reactions.
  • Step 1 the product of the hydrolyzed dihydrocyanopyran (Step 1) exists as an equilibrium mixture of the aldehyde, monocyanhydrin, and the cyclic hydroxy compound, 2-cyano-6hydroxytetra 'hydropyran. It is believed that the aldehyde form is selectively reduced in Step II thus shifting the equilibrium away from the cyclic hydroxy compound.
  • Acidic catalysts useful in the reaction of this invention include, but are not limited to, sulfuric acid, hydrochloric acid, other halogen acids, phosphoric acid; acid salts such as ammonium bisulfate, sodium bisulfate, sodium acid phosphate, and the like.
  • Cation exchange resins in their acid forms such as sulfonated styrene-divinyl benzene copolymers may also be used and such materials include Amberlyst-IS, Dowex-SO, Amberlyte-400, IR-20 and the like.
  • Ammonium bisulfate is the preferred hydrolysis catalyst in the instant invention.
  • the rate of hydrolysis of dihydrocyanopyran to glutaraldehyde monocyanhydrin depends upon temperature and degree of acidity. The higher the temperature and the greater the acidity, the shorter the timerequired for reaction to a given conversionfFor instance, at C. a minimum of 0.05 N strong mineral acid, such as sulfuric, is required in order to achieve hydrolysis in a reasonable length of time, whereas at room temperature an acidity of 2.0 N strong acid is necessary for practical hydrolysis rates. With 5 or 6 N strong acid, hydrolysis is completed in a matter of a few minutes.
  • the preferred reaction temperatures range from about room temperature to C. or slightly higher.
  • dihydrocyanopyran is fed to the hydrolysis reaction mixture in proportions such that the resulting monocyanhydrin of glutaraldehydeis soluble in the reaction medium and for an aqueous acid medium this isgenerally about 3040% by Weight.
  • a divided or an undivided cell may be used in the electrolytic reduction step, there is some preference for the use of a divided cell because some dihy' droxycaproic acid forms in the undivided cell by anodic hydrolysis of the nitrile group.
  • the dihydroxycaproic acid will probably impede dihydroxycapronitrile formation and crystallization. It is estimated that approximately onethird of the dihydroxycapronitrile produced by electrolysis in an undivided cell is hydrolyzed to the hydroxy acid.
  • a cationic permselective ion exchange resin be utilized. Any commercially available permselective cationic membrane such as Permutit 3142 or AMF-ion C102 would be suitable.
  • the preferred cathode composition is lead.
  • the cathode material maybe any conductive material that is passive under the influence of the cathode voltage as for example, cadmium, mercury, steel, iron, nickel and the like. Material selected for the anode must be resistant to the action of strong acids under anodic oxygen.
  • the anode is composed of lead dioxide or platinum.
  • the same acid medium that is employed in the hydrolysis may also be employed as the electrolyte. Again ammonium bisulfate is preferred.
  • concentration of the acid in the electrolyte solution is controlled by three factors. Sutficient acid must be present to provide conductivity and to aid solubilization of the monocyanhydrin of glutaraldehyde in the electrolyte at practical levels, e.g., in amounts of about 1 to 3 moles. The loss of excess acid in the separation of dihydroxycapronitrile from the reaction medium should be minimized. If dihydroxycapronitrile is recovered by means of an immiscible solvent, the use of excess acid will tend to solubilize the solvent. It is therefore preferred that the acidity of the electrolyte be in the range equivalent to from about .05 moles of sulfuric acid per liter or a normality of 0.1 up to 10 moles of sulfuric acid per liter or a normality of 20.
  • the electrolytic reduction is usually carried out at temperatures ranging fi'om about room temperature to about 45 C. However, temperatures of from 20 C. to 60 C. are operable.
  • the current densities in the electrolytic cell may vary widely. Generally the current density should fall within a range of 5 to 100 amps per square foot and a range of 20 to 50 amps per square foot is preferred. Theoretically, at least two Faradays of electricity are required to reduce one mole of the monocyanhydrin of glutaraldehyde to one mole of dihydroxycapronitrile.
  • the dihydroxycapronitrile produced by the present process is a known compound which is useful in some cases as a solvent and also as an intermediate glycol material in the preparation of alkyd resins by condensation with a dibasic organic acid or its anhydride.
  • the analytical determination of the monocyanhydrin of glutaraldehyde was carried out by adding excess hydroxylamine hydrochloride solution to an appropriately sized sample. Reaction of the aldehyde with hydroxylamine caused the liberation of hydrogen chloride which was determined by titration with standard base.
  • the Amberlyst 15 resin appearing in Table I is a sulfonated copolymer of styrene and divinyl benzene.
  • EXAMPLE II The electrolytic reduction Step II is illustrated in this example.
  • Two different electrolysis cells were used in conducting the experiments.
  • One cell consisted of two, threeinch diameter cylindrical plastic sections 1 /2" thick and /s" thick sandwiched together with disc electrodes at each end.
  • a semipermeable sulfonated styrene-divinyl benzene copolymer membrane supported on a polyester web (Permutit 3142) was sandwiched between using rubber gaskets for sealing. The entire assembly was held together in an insulated wood vise.
  • a mechanically driven angular glass rod provided stirring in the larger compartment which served as the cathode chamber. Electrical connections were made by clips to ears on the electrodes.
  • a sixvolt adjustable DC. power supply and suitable volt meter and am-meter Were also in the circuit.
  • the second cell was designed so that many cells could be stacked together in a minimum space. Flow-through provided stirring, and cell circuitry was the same as for the cell described above. In operating either cell, the electrolyte was charged to both chambers simultaneously. The monocyanhydrin of glutaraldehyde was added either gradually to the catholyte or was present initially. Experiments were conducted and remained at current and voltages where little or no cathode gas ing took place. The experiments were continued to a predetermined Faraday/ monocyanhydrin of glutaraldehyde ratio. In the second cell, circulation to and from the reservoir occurred at such a rate that the cell residence time was approximately 30 seconds. The circulation was on the order of 300 cc. per minute.
  • the acid catalyst is a member selected from the group consisting of sulfuric acid, hydrochloric acid, other halogen acids, phosphoric acid, sodium bisulfate, ammonium bisulfate, sodium acid phosphate, and cation exchange resins in the acid form.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Description

United States Patent 3,325,381 ELECTROLYTIC PROCESS FOR PRODUCING DIHYDROXYCAPRONITRILE Robert W. Foreman, Chagrin Falls, Ohio, assignor to The Standard Oil Company, Cleveland, Ohio, a c0rporation of Ohio No Drawing. Filed Feb. 3, 1964, Ser. No. 342,264 12 Claims. (Cl. 204-77) The present invention relates to a process for the production of dihydroxycapronitrile by the hydrolysis of dihydrocyanopyran to glutaraldehyde monocyanhydrin and the reduction of glutaraldehyde monocyanhydrin to dihydroxycapronitrile.
In the present invention 3,4-dihydro-2-cyano-2H-pyran or sometimes referred to herein simply as dihydrocyanopyran, which can be prepared from acrolein and acrylonitrile as described in my copending US. patent application, Ser. No. 251,056, filed Jan. 14, 1963, now Patent No. 3,153,052, is hydrolyzed in an aqueous solution of an acid salt to the monocyanhydrin of glutaraldehyde which is then reduced to 2,S-dihydroxycapronitrile in an electrochemical reaction by the following steps:
Step I The hydrolysis reaction may be carried out in a dilute aqueous solution of an acid, an acid salt or in the presence of a cation exchange material. The acid, acid salt or cation exchange material is a catalyst and is not consumed in the reaction. Preferably a dilute aqueous solution of an acid sulfate is utilized which later also may serve as the electrolyte in the electrolytic reduction step of the process. Such an electrolyte can be recycled after removal of the dihydroxycapronitrile, thereby simplifying the process and reducing the consumption of acidic catalyst.
The electrolytic reduction of the glutaraldehyde monocyanhydrin may be conveniently carried out in an undivided cell, using preferably, a lead cathode and a lead dioxide or platinum anode. If a divider is used to separate the cathode and anode compartments, a permselective cation exchange membrane is preferred. The monocyanhydrin of glutaraldehyde is fed to the cathode compartment and the product, dihydroxycapronitrile, may be recovered from the aqueous catholyte by means of solvent extraction. The electrolyte can then be recycled to the hydrolysis reaction or to the electrolytic cells as desired. Selective catalytic hydrogenation of the aldehyde group of the monocyanhydrin of glutaraldehyde is difficult. With Raney nickel, for instance, high temperatures and pressures are required to catalyze the hydrogenation, and then the nitrile group is hydrogenated in preference to the aldehyde group. Unexpectedly, the most successful means for the conversion is by electrolytic reduction.
The hydrolysis Step I and the electrochemical reduction Step II may be conducted in separate or the same reaction vessels in a sequential or simultaneous manner and still be within the scope of the present invention. If the two steps are carried out simultaneously, however, reaction conditions must be adjusted to maximize the yields in both reactions.
As shown by equation earlier, the product of the hydrolyzed dihydrocyanopyran (Step 1) exists as an equilibrium mixture of the aldehyde, monocyanhydrin, and the cyclic hydroxy compound, 2-cyano-6hydroxytetra 'hydropyran. It is believed that the aldehyde form is selectively reduced in Step II thus shifting the equilibrium away from the cyclic hydroxy compound.
In the hydrolysis Step I any water soluble acidic material having an acid strength equal to or greater than that of acetic acid (K=l.75 l0' is suitable as a catalyst. Acidic catalysts useful in the reaction of this invention include, but are not limited to, sulfuric acid, hydrochloric acid, other halogen acids, phosphoric acid; acid salts such as ammonium bisulfate, sodium bisulfate, sodium acid phosphate, and the like. Cation exchange resins in their acid forms such as sulfonated styrene-divinyl benzene copolymers may also be used and such materials include Amberlyst-IS, Dowex-SO, Amberlyte-400, IR-20 and the like. Ammonium bisulfate is the preferred hydrolysis catalyst in the instant invention.
The rate of hydrolysis of dihydrocyanopyran to glutaraldehyde monocyanhydrin depends upon temperature and degree of acidity. The higher the temperature and the greater the acidity, the shorter the timerequired for reaction to a given conversionfFor instance, at C. a minimum of 0.05 N strong mineral acid, such as sulfuric, is required in order to achieve hydrolysis in a reasonable length of time, whereas at room temperature an acidity of 2.0 N strong acid is necessary for practical hydrolysis rates. With 5 or 6 N strong acid, hydrolysis is completed in a matter of a few minutes. The preferred reaction temperatures range from about room temperature to C. or slightly higher. Preferably dihydrocyanopyran is fed to the hydrolysis reaction mixture in proportions such that the resulting monocyanhydrin of glutaraldehydeis soluble in the reaction medium and for an aqueous acid medium this isgenerally about 3040% by Weight. I
Although either a divided or an undivided cell may be used in the electrolytic reduction step, there is some preference for the use of a divided cell because some dihy' droxycaproic acid forms in the undivided cell by anodic hydrolysis of the nitrile group. The dihydroxycaproic acid will probably impede dihydroxycapronitrile formation and crystallization. It is estimated that approximately onethird of the dihydroxycapronitrile produced by electrolysis in an undivided cell is hydrolyzed to the hydroxy acid.
It the membrane is used to separate the reactions at the anode and the cathode, it is preferred that a cationic permselective ion exchange resin be utilized. Any commercially available permselective cationic membrane such as Permutit 3142 or AMF-ion C102 would be suitable.
The preferred cathode composition is lead. Actually, the cathode material maybe any conductive material that is passive under the influence of the cathode voltage as for example, cadmium, mercury, steel, iron, nickel and the like. Material selected for the anode must be resistant to the action of strong acids under anodic oxygen. Preferably the anode is composed of lead dioxide or platinum.
For a more simplified and economical operation, the same acid medium that is employed in the hydrolysis may also be employed as the electrolyte. Again ammonium bisulfate is preferred. The concentration of the acid in the electrolyte solution is controlled by three factors. Sutficient acid must be present to provide conductivity and to aid solubilization of the monocyanhydrin of glutaraldehyde in the electrolyte at practical levels, e.g., in amounts of about 1 to 3 moles. The loss of excess acid in the separation of dihydroxycapronitrile from the reaction medium should be minimized. If dihydroxycapronitrile is recovered by means of an immiscible solvent, the use of excess acid will tend to solubilize the solvent. It is therefore preferred that the acidity of the electrolyte be in the range equivalent to from about .05 moles of sulfuric acid per liter or a normality of 0.1 up to 10 moles of sulfuric acid per liter or a normality of 20.
The electrolytic reduction is usually carried out at temperatures ranging fi'om about room temperature to about 45 C. However, temperatures of from 20 C. to 60 C. are operable.
The current densities in the electrolytic cell may vary widely. Generally the current density should fall within a range of 5 to 100 amps per square foot and a range of 20 to 50 amps per square foot is preferred. Theoretically, at least two Faradays of electricity are required to reduce one mole of the monocyanhydrin of glutaraldehyde to one mole of dihydroxycapronitrile.
The dihydroxycapronitrile produced by the present process is a known compound which is useful in some cases as a solvent and also as an intermediate glycol material in the preparation of alkyd resins by condensation with a dibasic organic acid or its anhydride.
The present invention is further illustrated in the following examples wherein the amounts of ingredients are expressed as parts by weight unless otherwise indicated.
EXAMPLE I Step I reactions employing various acids and acid salts at varying concentrations and reaction conditions are illustrated in detail in Table I. In each case the conversion of dihydrocyanopyran to the equilibrium mixture of the monocyanhydrin of glutaraldehyde and the tetrahydrohydroxycyanopyran was complete.
The hydrolysis of dihydrocyanopyran was conducted either in a mechanically stirred flask or the agitation was supplied by shaking the reaction flask. Water bath heating was used until the visible dissolution of dihydrocyanopyran occurred and then the hydrolysis continued for about to 30 minutes thereafter. When Amberlyst resin was used, it was converted to the acid form and then washed with water prior to use in the hydrolysis reaction. v20 grams of resin per 100 ml. of water and 0.1 mole of dihydrocyanopyran were used. Trc monocyanhydrin of glutaraldehyde was isolated by neutralizing the hydrolyzed product with sodium carbonate containing some sodium sulfate or sodium chloride followed by extraction with ether. The ether was then removed carefully from the hydrolysis product at near room temperature and under nitrogen.
The analytical determination of the monocyanhydrin of glutaraldehyde was carried out by adding excess hydroxylamine hydrochloride solution to an appropriately sized sample. Reaction of the aldehyde with hydroxylamine caused the liberation of hydrogen chloride which was determined by titration with standard base. The Amberlyst 15 resin appearing in Table I is a sulfonated copolymer of styrene and divinyl benzene.
EXAMPLE II The electrolytic reduction Step II is illustrated in this example. Two different electrolysis cells were used in conducting the experiments. One cell consisted of two, threeinch diameter cylindrical plastic sections 1 /2" thick and /s" thick sandwiched together with disc electrodes at each end. A semipermeable sulfonated styrene-divinyl benzene copolymer membrane supported on a polyester web (Permutit 3142) was sandwiched between using rubber gaskets for sealing. The entire assembly was held together in an insulated wood vise. A mechanically driven angular glass rod provided stirring in the larger compartment which served as the cathode chamber. Electrical connections were made by clips to ears on the electrodes. A sixvolt adjustable DC. power supply and suitable volt meter and am-meter Were also in the circuit.
The second cell was designed so that many cells could be stacked together in a minimum space. Flow-through provided stirring, and cell circuitry was the same as for the cell described above. In operating either cell, the electrolyte was charged to both chambers simultaneously. The monocyanhydrin of glutaraldehyde was added either gradually to the catholyte or was present initially. Experiments were conducted and remained at current and voltages where little or no cathode gas ing took place. The experiments were continued to a predetermined Faraday/ monocyanhydrin of glutaraldehyde ratio. In the second cell, circulation to and from the reservoir occurred at such a rate that the cell residence time was approximately 30 seconds. The circulation was on the order of 300 cc. per minute.
TABLE I. HYDROLYSIS CONDITIONS Hydrolysis Medium Temp., Time, G. DHCP, Mixing Procedure Post Treatment Recovery 0. Hours 100 cc. (Percent) 2 0.1 N H01 3.0 25 Ozree stirred flask Neut. to pH=2, add NaCl,
ether extracted. 0.1NHO1 80 2.0 25 do 92 0.1 N H01- 90 1.0 10 Neut. to pH=4, not salted, -72
ether extracted. 0.5 N HCl 1.67 15- 6 1O Hydrogenated aqueous solution as produced. 0,02 N H 3. 5 10 d0 Neut. to pH=2, add NaCl, 75
ether extracted. 120 1. 0 10 Heated in earius tube-not Salted w. NaOl, either exshaken. tracted. 0.05 N HzSO; 90 2.0 10. 9 Stirred flask. Neut. w. OaCOa filtered, 89
ether extracted. 0.1 N H SO; 90 .75 Neut. to pH=3, Na SO4 added, 75
. ether extracted. 0.5 N 112804 90 1.0 Neut. to pI-I=4 1.0 M NaHSOr 90 0. 5 o None H O+5 w./w. Percent 25 48 Mechanical shak Ether extracted. 76
Amberlyst-l5 Acid Ion Exchange Resin. 7 HzO-l-fi w./w. Percent 0.20 10. 9 Stirred flask under reflux Deeply ether extracted 88 Amber1yst-15 Acid Ion Exchange Resin.
1 Dihydrocyanopyran.
= Not determined.
Experimental examples showing the feasibility of a number of different electrodes, electrolytes, and reaction conditions are summarized in Table II. The analysis of unreacted monocyanhydrin of glutaraldehyde and dihydroxycapr-onitrile was made as the electrolysis proceeded. The analytical procedure for the determination of dihydroxycapronitrile included adding an excess of 0.1 normal silver nitrate to a suitable size sample, adjusting the pH with caustic to 7.5 until the pH remained at that level for a minimum of five minutes. The silver cyanide produced was removed by filtration, the pH was adjusted to the acid side with dilute nitric acid, and the excess silver ion was determined by titration with standard potassium thiocyanate to a ferric alum end point. If too much sulfate was present in the sample, it was removed as barium sulfate before proceeding with the analysis.
In Table II the Faraday-to-mole monocyanhydrin of glutaraldehyde ratio was slightly greater than 2. The conversions varied from about 69 to 100%.
4. The process of claim 3 wherein the hydrolysis is carried out at a temperature in the range of from about room temperature to slightly above 100 C.
5. The process of claim 4 wherein the electrolytic reduction is carried out at a temperature in the range of from about to C.
6. The process of claim 5 wherein the electrolytic reduction is carried out at a current density of from 5 to 100 amps. per square foot.
7. The process of claim 6 wherein the acid catalyst is present in a concentration of from 0.5 N to 20 N.
8. The process of claim 7 wherein the acid catalyst is a member selected from the group consisting of sulfuric acid, hydrochloric acid, other halogen acids, phosphoric acid, sodium bisulfate, ammonium bisulfate, sodium acid phosphate, and cation exchange resins in the acid form.
9. The process of claim 8 wherein the acid catalyst is hydrochloric acid.
TABLE II Feed Final Electrolyte Cell 2 IMOHG, 100 cc. MCHG 1 Source Addition Method Electrolyte Catholyte plus Cone. Anolyte plus Cone. Cathode Temp. C.
l Molar NaI-ISOi hydrolyzate All in at start 11. 4 1.0 M NaHSO 1 M NaHSOi I-Ig, Pb
(94% yield from DHCP Amberlyst hydrolyzed do 10. 6 207 cc. 1.0 N H cc. 1.0 N I'I2SOJ Cd 32-40 DHOP -86.4% yield (.1
mole/100 cc./20 g. resin). Concd (in vacuo) aq. soln Added gradually 7. 82 cc. 1.0 M NaT-ISO; at cc. 1.0 M NaHSO4 Fe (Steel) 30-40 from Amberlyst hydrolystart. Final calcd v0l.=
mate-84% yield. Yield 0 cc.
85% but not accurately determined. Concd aq. Amberlyst .d0 10. 0 140 cc. 1.0 M NH4HSO4 at 140 cc. 1.0 M Cd 27-38 hydrolyzate (82% yield) start. Final calcd vol.= N HlHSOi.
cone. to 2.6 M in aldehyde. 200 cc. 1 M NH HSO4 hydrol. Continuous cir- 10.8 1,500 mi. 1 M NH HSO 120 ml. 1 M Pb, not pre- Ambient.
DHOP 2 (92% yield). culation with MGHG'.1 NH4HSO4. eondit.
withdrawals plus addns.
1 Monocyanhydrin of Glutaraldehydc. 2 Dihydrocyanopyran.
I claim:
1. The process for the manufacture of 2,5-dihydroxycapronitrile comprising hydrolyzing 3,4-dihydro-2-cyanor ZH-pyran in an aqueous medium in the presence of an acid catalyst to form the rnonocyanhydrin of glutaraldehyde and electrolytically reducing the monocyanhydrin of glutaraldehyde in an aqueous medium in the presence of an electrolyte to 2,S-dihydroxycapronitrile.
2. The process of claim 1 wherein the acid catalyst is a material which has an acidity of at least K=1.75 10- No references cited.
JOHN H. MACK, Primary Examiner.
3. The process of claim 2 wherein the electrolyte i D. R. VALENTINE, Assistant Examiner.
the same as the acid catalyst.

Claims (1)

1. THE PROCESS FOR THE MANUFACTURE OF 2,5-DIHYDROXYCAPRONITRILE COMPRISING HYDROLYZING 3,4-DIHYDRO-2-CYANO2H-PYRAN IN AN AQUEOUS MEDIUM IN THE PRESENCE OF AN ACID CATALYST TO FORM THE MONOCYANHYDRIN OF GLUTARALDEHYDE AND ELECTROLYTICALLY REDUCING THE MONOCYANHYDRIN OF GLUTARALDEHYDE IN AN AQUEOUS MEDIUM IN THE PRESENCE OF AN ELECTROLYTE TO 2,5-DIHYDROXYCAPRONITRILE.
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