Description:FIELD OF THE INVENTION
[001] The invention relates to the process of producing 2-Chloro-1,1 dimethoxyethane or Chloroacetaldehyde dimethyl acetal (CADMA) and more particularly relates to a continuous process of manufacturing CADMA devoid of MeOCl formation and comes out with a technology that minimized the use of Cl2.
BACKGROUND OF THE INVENTION
[002] Chloroacetaldehyde dimethyl acetal (CADMA) belongs to the class of substituted halo acetals. CADMA is a colourless liquid used in the preparation of pharmaceutical intermediates, pesticides, and flavouring agents. The synthesis of CADMA involves chlorinating vinyl acetate with gaseous chlorine and the 1, 2 dichloroethyl acetate thus obtained is treated with methanol to yield CADMA.
[003] Chloroacetaldehyde acetals are usually obtained by chlorinating vinyl compounds such as vinyl chloride, vinyl ether or vinyl esters in alcoholic medium (Ullmann, Enzylopadie der technischen Chemie, 4th edition 1975, volume 9, page 375). Chloroacetaldehyde dimethyl acetal manufacturing from vinyl chloride is not a very suitable method as it produces considerable amounts of by products such as 1,1,2-trichloroethane which have similar boiling points and are difficult to get separated from the desired final products. Moreover, toxicity due to vinyl chloride demands expensive safety protocols to be followed while scaling-up the process industrially.
[004] When vinyl ether is used, the process cannot be scaled-up industrially as the starting materials are not readily available and chlorination necessitated the presence of alkali or alkaline earth metal oxides, carbonates, bicarbonates, alcoholates or hydroxides to yield better results. Further when Calcium oxide is used, the yield gets drastically affected due to low solubility calcium oxide in methyl alcohol.
[005] Prior art contains many references that have dealt with syntheses of substituted haloacetals.
[006] E. M. Filachione concluded that methyl haloacetals are giving quite low yields when compared to ethyl haloacetals and moreover methyl haloacetals are not economical as the manufacturing process involves enormous amount of solvent usage leading to poor yields (Am. Chem. Soc., Vol. 61, (1939), pages 1705-06).
[007] US pat.2,550,637 revealed a process of producing acetals of beta-haloaldehydes which comprises reacting an alpha, beta-ethylenically unsaturated ether selected from the group consisting of alkyl and aryl-alpha, beta-ethylenically unsaturated ethers with chlorine. The alpha, beta-ethylenically unsaturated ether is a lower alkyl-alpha, beta-ethylenically unsaturated ether.
[008] U.S. Pat. No. 3,379,772 disclosed a process of producing acetals of B-haloaldehydes which comprises reacting at a temperature of from 60 C. to 5 C. an alpha, beta-ethylenically unsaturated ether with an alcohol and halogen selected from the group consisting of chlorine and bromine and an alkaline agent, the improvement which comprises utilizing as the alkaline agent, calcium oxide in a particle size of to 325 screen mesh.
[009] U.S. Pat. No. 2,330,570 disclosed a method of preparing a halo acetal which comprises introducing an elemental halogen selected from the group consisting of bromine and chlorine into a mixture or vinyl acetate and a monohydric primary alcohol.
[010] U.S. Pat. No. 2,411,826 disclosed a method of preparing a halo acetal which comprises introducing an elemental halogen selected 'from the group consisting of bromine and chlorine into a mixture of vinyl acetate and an' alcohol.
[011] JP 2003073322A disclosed a method for producing a halogenoacetaldehyde dialkyl acetal by continuously introducing vinyl acetate and a halogen into an alcohol. /1.5 to 1/5 equivalent and introducing vinyl acetate and halogen in substantially equimolar amounts over 4 hours or more. It also disclosed a halogenoacetaldehyde obtained by adding the reaction mixture obtained by the above method to a suspension of an oxide of a metal of Group IIa in an organic solvent, thereby neutralizing the reaction mixture. A method for separating a halogenoacetaldehyde dialkyl acetal, comprising distilling an organic layer containing a dialkyl acetal, or washing the organic layer with an aqueous solution of a metal carbonate, followed by distillation is also given.

[012] U.S. Pat. No. 4,440,959 disclosed manufacture of chloroacetaldehyde dimethyl acetal in which low-boiling constituents are distilled off completely or partially from the reaction mixture obtained by the reaction of vinyl acetate and chlorine in stoichiometric amounts in the presence of excess methanol, when the addition of chlorine is complete. The remaining liquid residue is neutralized with solid substances, such as oxides or carbonates of calcium and magnesium, while maintaining a temperature of from 200 to 600 C., until the aqueous extract has a pH of greater than 5.The separation of methyl haloacetals using Calcium oxide was not achieved successfully from one layer which then required another method involving usage of Methyl acetate which is also a by-product of the reaction to separate out methyl haloacetals from previously separated aqueous layer.
[013] Most of the prior art references disclosed the synthesis of haloacetaldehyde dialkyl acetal using vinyl acetate and halogen in alcoholic medium. The crude acetal thus obtained from the reaction between vinyl acetate and halogen in alcoholic medium was isolated from the mixture in different ways, such as quenching with water followed by extracting the acetal layer with a water-immiscible solvent such as ether, benzene, or chloroform. The resultant organic extract was then washed with water or an aqueous alkaline solution such as sodium hydroxide solution to remove acid and other water-soluble by-products, which was followed by distillation to obtain the pure acetal.
[014] Though the prior art contains similar methods of manufacturing of 2-chloro-1,1-dimethoxyethane or chloroacetaldehyde dimethyl acetal (CADMA), most of them are dealing with either batch processes or semi-continuous processes. Moreover the prior art processes are associated with wastage of solvents, long duration of reaction times, use of excess chlorine, and consequently, release of elemental chlorine into the environment that is toxic (Chlorine Gas Toxicity, Ashkan Morim 1, Gregory T. Guldne,r In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan, 2022 Jun 27 PMID: 30725898; Bookshelf ID: NBK537213) , in addition to the formation of highly explosive MeOCl (Chemical Safety Board Releases Final Report into Fatal Tank Explosions at the Midland Resource Recovery (MRR) Facility in Philippi, West Virginia, U.S. Chemical Safety Board, December 17, 2019 ). Hence there is every need to close-in these loopholes and come out with a process for the continuous manufacturing of CADMA with minimal wastage of the reactants, reagents, solvents, and neutralizing agents, with higher yields of CADMA, and considerable reduction in, MeOCl formation and Cl2 release into the environment. These factors necessitated to come out with the instant invention of “A PROCESS FOR CONTINUOUS MANUFACTURING OF 2-CHLORO-1,1-DIMETHYOXYETHANE”

[015] The essential elements of the instant invention included considerable reduction of elemental chlorine release into the atmosphere and explosivity of the operation due to MeOCl formation. Other notable features of the instant invention are minimal usage of the solvents compared to the previous processes, addition of water-immiscible organic solvents, and distilling off low-boiling impurities. Neutralization is accomplished by the usage of aqueous/methanolic ammonia or anhydrous ammonia.
[016] The exemplary aspects of various embodiments of the invention are disclosed in the summary of the invention and all the essential aspects related to various embodiments of the invention are described in a detailed manner in the following paragraphs with specific references towards the corresponding figures as given hereunder. All the prior art references are incorporated hereby in their entirety and for reference-sake and in no way taking away the novelty of the instant invention. The various aspects of the instant invention disclosed here are definitely an improvement over the existing prior art and further stress upon the inventorship, novelty and applicability of the instant invention.
SUMMARY OF THE INVENTION
[017] The exemplary embodiment of the invention discloses a process for the continuous manufacturing of 2-Chloro-1,1 dimethyoxyethane or chloroacetaldehyde dimethyl acetal (CADMA) by passing chlorine gas along with vinyl acetate at -10 to 60 degrees Celsius in a continuous flow reactor.
[018] One preferred embodiment of the invention discloses reaction mass further reacting with methanol in another continuous or flow reactor to get 2-Chloro-1,1 dimethyoxyethane. The organic mass thus obtained after methanol reaction is neutralized with liquid base and the organic layer is separated. The by-products methanol and methyl acetate in aqueous layer are then recovered. The organic layer containing product along with remaining methanol and methyl acetate is evaporated to get crude product which is then washed with aqueous base to remove close-boiling impurity. The organic layer is the separated and then isolated by distillation under vacuum at 55 to 75 degrees Celsius.
[019] One more exemplary embodiment of the invention discloses the instant invention comprising two steps, wherein the first step eliminates the risk of methyl hypochlorite formation and improves yield and further contact of reaction mass over increasing concentration of water is avoided by conducting the step 2 reaction in flow or in continuous mode.
[020] Yet another embodiment of the invention discloses a sustainable continuous flow process with residence time ranging from 1 to 10 minutes for the completion of first reaction which is carried out at a temperature of -10oC to 60 oC.
[021] The invention further discloses an inherently safe process which avoids methanol and chlorine contact.
[022] The various embodiments of the instant invention are described in detail with the help of the accompanying drawings, drawing inferences to the specific aspects of the individual embodiments of the invention in the following sections.
OBJECTIVES OF THE INVENTION
1. To come out with a two-stepped process for continuous manufacturing of 2-Chloro-1,1 dimethoxyethane or chloroacetaldehyde dimethyl acetal (CADMA) by passing chlorine gas along with vinyl acetate at in a continuous flow reactor with minimized wastage of chlorine.
2. To come out with a continuous flow process for manufacturing 2-chloro-1,1-dimethoxyethane comprising two steps, wherein the first step eliminates the risk of methyl hypochlorite formation and improves yield and further contact of reaction mass over increasing concentration of water is avoided by conducting the step 2 reaction in flow or in continuous mode.
3. To come out with a technology of manufacturing 2-chloro-1,1-dimethoxyethane with reduced toxicity due to low Cl2 emissions, wastage of solvents and neutralizing reagents and further reduces formation of MeOCl a violently decomposing by product.
DETAILED DESCRIPTION OF THE INVENTION
[023] The examples of the apparatus discussed herein are not limited in application to the details of construction and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. It will be understood by one of skill in the art that the apparatus is capable of implementation in other embodiments and of being practiced or carried out in various ways. Examples of specific embodiments are provided herein for illustrative purposes only and are not intended to be limiting. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
[024] Any references to examples, embodiments, components, elements or acts of the apparatus herein referred to in the singular may also embrace embodiments including a plurality, and any references in plural to any embodiment, component, element, or act herein may also embrace embodiments including only a singularity (or unitary structure). References in the singular or plural form are not intended to limit the presently disclosed apparatus, its components, acts, or elements.
[025] The use herein of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. References to “or” may be construed as inclusive so that any terms described using “or” may indicate any of a single, more than one, and all of the described terms. The various embodiments of invention are described in detail herein and the various aspects of the invention are disclosed below.
[026] DEFINITIONS
CADMA is chloroacetaldehyde dimethyl acetal.
VAM is Vinyl Acetate(monomer).
Chlorination is treating with elemental Cl2.
Transesterification is interchange of alcohols from an ester.
Alcoholysis is treating with an organic compound having at least one -OH functional group.
MeOCl is methyl hypochlorite.
Vinyl means an organic compound having at least one -CH2=CH- linkage in its structure.
Flow reactor is a continuous tubular reactor consisting of static mixers.
FFE is Falling film evaporator.
IDEX is a supplier of PFA fittings for flow reactors.
TSMR is a jacketed Tubular Static Mixer Reactor (in house design): with provision to feed multiple streams on process side and with a jacket to circulate utility oil to maintain desired temperature in the reaction.
CSTR is Continuous Stirred tank reactor.
AFR® is Corning’s Advance Flow Reactor®.

6.4 RT impurity is an unidentified impurity occurring at 6.4 Retention time in the chromatogram.
Rag layer neutralization is the neutralization process of a layer that is formed at the interface of organic and aqueous layers in liquid-liquid extraction process.
Barg is a pressure unit equivalent to Bar+gauge.
GC is gas-phase chromatographic separation technique.
GC-MS is Gas chromatography coupled with Mass spectrometry used for simultaneous separation and identification of the constituents of the experimental sample.
[027] The following paragraphs give a detailed description of the development of a continuous flow-process for manufacturing CADMA in an economical, environmentally friendly manner with improved yields and reduced wastage of Cl2 .
[028] The purity of the final product and percentage yield of CADMA are obtained by performing GC analysis and GC-MS analysis of the reaction products at regular intervals at different experimental conditions. The conditions under which the GC and GC-MS analyses were performed are given below. GC and GC-MS analyses of the experimental samples are done under similar conditions taking identical columns, carrier gas and sample volumes at similar temperatures.
INSTRUMENTAL ANALYSIS:
[029] GC ANALYSIS:
GC analysis of the experimental samples was done by maintaining the GC at the following conditions: Keeping the Column: DB-624 30m, 0.32mm, 1.8µm, ( P.NO. 123-1334UI) at an Inlet temperature of 220 °C; Injection at a Split ratio of 50:1; carrier gas Nitrogen at a flow rate of 2.5ml/min; Injection volume of 0.5 microlitre; Detector temperature at 260° C; Airflow of 400mL/min; H2 flow of 40mL/min; using DMF as diluent; Column oven temperature at 40° C, holding for 2 min; and the makeup gas Nitrogen flow at 25mL/min.
[030] GC-MS ANALYSIS:
GC-MS analysis of the experimental samples was done on a quadrupole MS using EI-detection method under similar GC conditions as given above to arrive at the purity of the reaction products.
[031] The CADMA process was carried out in both commercial and TSMR reactors to arrive at the suitability of such reactors to perform CADMA synthesis to obtain the final product with high purity and higher percentage of yield of the final product with minimal wastage of the reactants and solvents. The following description throws light upon various experimental methods, reactor selection methods and describes the best method of synthesis of CADMA.
METHODOLOGY
[032] The process of producing CADMA involves chlorination of Vinyl acetate (VAM) with chlorine gas and treating the chlorinated ester formed with methanol for alcoholysis. Methyl acetate is formed as by-product by transesterification of the ester with methanol. HCl and water are also formed as by-products in this process. The organic mass obtained after alcoholysis is then subjected to neutralization of HCl with ammonia and the layers are separated. The organic layer is then distilled to remove excess methanol and methyl acetate. The crude organic material obtained from reboiler is given an aqueous wash to remove close boiling impurity and the layers are separated. The organic layer containing crude CADMA is distilled to obtain the pure product.
[033] Literature reports strongly indicated the formation of highly explosive methyl hypochlorite (MeOCl) due to the interaction of methanol with chlorine. Methanol should therefore not to be contacted with chlorine. This safety hazard associated with the CADMA process involving all 3 reactants mixing together described in the prior art formed the requisite for the instant invention, with the objective to develop a safe, economical, and easy-to-commercialize process. One aspect of the invention is to carry out the reaction in 2 steps wherein vinyl acetate is reacted with chlorine in a TSMR which has excellent gas liquid mixing and heat transfer capability. The flow process in TSMR also allows for effective control on excess chlorine moles that need to be used (compared to published batch processes) in the first step. In this system, due to excellent gas-liquid mass transfer, very small amount of chlorine (if at all) remains unreacted.
[034] The reaction mass is passed through a falling film evaporator which acts as a gas separator to remove unreacted chlorine from the reaction mass. The advantage of this aspect of the invention is Chlorine removal from the reaction mass prior to addition of alcohol, which avoids formation of methyl hypochlorite. The other advantage is better separation of chlorine which can be easily scrubbed downstream. Chlorine when unseparated from reaction mass will get mixed with hydrogen chloride gas formed during the next step alcoholysis reaction occurring with methanol. This will make separation of chlorine from HCl gas difficult and can cause fugitive emission of chlorine.
[035] The reaction mass containing the ester is treated with methanol in a continuous flow reactor to get CADMA for a sufficient residence time. The reaction mass is then neutralized with ammonia base forming two liquid layers at around pH of 7. The organic layer is then separated from the aqueous layer and subjected to distillation for removal of excess methanol and methyl acetate. The residue obtained is then washed with aqueous ammonia to remove close boiling 6.4-minute RT impurity. The organic layer after removal of 6.4-minute impurity is then distilled to get pure product. The structure and physical parameters of the final product are given in Table 1.
Table 1: Structure and properties of CADMA
Structure
IUPAC Name 2-Chloro-1,1-dimethoxyethane
CAS Number 97-97-2
Molecular Weight 124.56
Molecular formula C4H9ClO2

[036] The following paragraphs describe in detail the development of a continuous process for obtaining CADMA
Process Description
Step 1 reaction
[037] In a continuous jacketed tubular reactor containing static mixer elements (TSMR), Vinyl acetate is fed through a pump with a liquid flowrate of 3.5 mL/minute to 5 mL/minute and chlorine gas is passed at 1.1 to 1.4 molar equivalents. The residence time is varied between 1.5 minutes and 12 minutes to state the robustness of the process. The temperature at the jacket of the tubular reactor is varied from -10 to 60 o C for optimizing the reaction. The reaction is maintained at back pressure between 0 to 5 barg. The reaction mass coming out of the tubular reactor is collected into a glass receiver after a falling film evaporator to remove the excess chlorine present in the system. The collection receiver is kept at same temperature as reaction after coming out of falling film evaporator.
[038] The collected reaction mass is passed into another continuous reactor for the step 2 reaction where methanol gets mixed. The robustness of the process is also checked by varying the methanol mole ratio between 3.6 to 5 times with respect to vinyl acetate, varying the temperature between -5 and 15 oC, varying the residence time between 30 to 150 minutes. The outcomes of different experiments have been summarised in table 2 given below. The HCl produced as by-product is neutralized with ammonium base. Several bases are screened for the neutralization reaction and ammonia has been finalised, based on the yield obtained, and operation-suitability. The organic layer obtained is further processed by distillation to remove methanol and methyl acetate. The crude product after treatment with aqueous ammonia is then distilled to get pure CADMA.
Table 2. Experimental Results of Continuous Process of CADMA.
Exp No Temp
oC Pressure
Barg Residence time, min VAM processed in g CADMA
Assay
(%) Weight of CADMA obtained (g) Yield W/W%
1 -5 2.2 2 150.3 28.6 157.19 72.3
2 0 2.3 2 75.3 25.2 71.85 66.0
3 -10 2 2.2 70.2 26.8 74.3 73.2
4 5 2.3 8 129 29.4 132.16 70.8
5 -5 2.2 2.2 150.3 28.6 157.19 72.3
6 -5 1 2 74.7 24.6 68.85 63.7
7 -5 3 2 76.7 29.5 77.93 70.3
8 -5 2.2 2 150.3 28.6 157.19 72.3
9 -5 2.2 1 78.4 30.4 82.43 72.6
10 -5 2 10.7 80.23 29.0 82.82 71.4
11 5 2.3 8 129 29.4 132.16 70.9

[039] It is understood from the reports of B.G.Yasnitskii and A.N.Androsov in “ Reversibility of the interaction of Chloroacetaldehyde and acetyl chloride” that, 1, 2 dichloroethyl acetate will be in equilibrium with Chloroacetaldehyde and acetyl chloride. The reaction therefore should be free from moisture to avoid further formation of Chloroacetaldehyde which will reduce the yield. The step 1 chlorination reaction when conducted at 5 o C can reach a temperature of 60 o C or even higher when the chilling circulation is unavailable at the mixing zone or at the outlet zone due to the heat of reaction. Enough care is also taken to avoid vinyl acetate polymerization at this stage of reaction. The reaction mass sample obtained after step 1 reaction is quenched with methanol and the sample is subjected to GC assay (CADMA assay). The molar yield of CADMA obtained in each case is presented in table 2. The table 2 illustrated step 1 experimental results obtained for different experimental parameters under consideration.
Step 2 reaction
[040] The temperature, pressure and residence time of step 2 reaction after step 1 chlorination reaction are maintained at the desired range between and are 5O to 20OC, 1 to 2 barg and 30 to 150 minutes respectively. It is observed from the experiments that methanol reaction is relatively lower exothermic than step 1 chlorination reaction. Alcoholysis occurs in step 2 with methanol and 1, 2 Di chloroethyl acetate. For every mole of 1, 2 dichloro intermediate, 3 moles of methanol will be used. 2 moles of methanol will be consumed in the acetal formation and 1 mole will be consumed to form for methyl acetate. Transesterification of acetate group also occurs in the reaction which gives methyl acetate. The table 3 shows the effect of time on Step 2 reaction
Table 3. Effect of time on Step 2 reaction.
Exp No Residence time minutes CADMA qty in aq. layer g CADMA in organic layer, g Total Weight of CADMA, g VAM processed, g Yield W/W%
12 40 0.53 0.31 0.84 1.49 38.8
13 55 0.40 0.89 1.30 1.54 58.3
14 80 0.32 1.14 1.46 1.65 72.2
15 105 0.37 1.03 1.40 1.34 72.2
16 120 0.45 1.65 2.10 1.83 79.6

[041] It can be observed from table 3 that the step 2 reaction is relatively slower than chlorination reaction, and the residence time of this reaction should be higher at the temperature being tested which is maintained at 15oC. The table 4 shows the experimental data obtained for methanol quantity requirement.
Table 4. Experimental results obtained for the quantity of methanol required.
Exp No Temp
oC MeOH
qty in mol Pressure
Barg VAM in g CADMA
Assay Org Qty Weight of CADMA obt. in g Yield W/W (%)
17 5 5 2.3 129 29.38 % 449.8 132.1 70.8
18 5 3.6 2.6 127.5 24.68 % 248 61.2 65.8
39.16 % 153.9 60.2
19 5 4 2.6 185.0 30.17 % 620.5 187.2 69.9

[042] The table 4 shows that the minimum quantity of methanol required for a better yield of CADMA is 4 mole equivalents. The temperature effect on step 2 reaction is also studied in a similar way by keeping the step 1 parameters such as residence time, temperature and equivalents’, constant and the results are given in Table 5.
Table 5. Effect of temperature on Step 2 reaction.
Exp No Temp
oC Pressure
Barg Time in minutes Yield W/W
20 -5 Atm 105 72.5
21 5 Atm 90 68.2
22 10 Atm 90 58.1

[043] It can be observed from the table that temperature has a significant effect and can lower the yield when the reaction temperature is increased.
Neutralization
[044] The reaction mass obtained from the step 2 reaction is neutralized with an yield-selective base. The bases screened are listed below in the table 6.
Table 6. Effect of different Base for neutralization on yield
Exp No Base used in the system Quantity of RM taken in g Solution % Qty of base weight in g VAM in g Yield W/W Reaction mass Yield W/W (%)
23 Aq. Sodium Carbonate 50.0 15% 110 ml 8.31 13.84 0.60 58.7
24 50.0 25% 66 ml 7.09 13.84 0.51 58.7
25 Aq. Sodium Bicarbonate 50.0 8% 231.5 g 5.91 13.84 0.43 58.7
26 Aq. Sodium hydroxide 50.0 15% 83.2 mL 7.44 13.84 0.53 58.7
27 Solid Calcium oxide 50.0 - 9 g Not easy to process 58.7
28 Sodium Carbonate solid addition + DCM 49.10 - 15.2 g 11.21 13.84 0.81 58.7
29 Sodium Carbonate Solid addition 49.60 - 7.67 13.84 0.55 58.7
30 NH3 gas+ DCM 114.70 - 10.77 13.99 0.77 68.4
31 MeOH ammonia – Exp 46 264.5 12% 200 ml 77.42 76.7 1.00 70.3

[045] It was found that ammonia neutralization is the most suitable option from amongst all the bases used for neutralization.
[046] The instant invention of two-stepped continuous flow process for the synthesis of 2-chloro-1,1-dimethoxyethane is novel and non-obvious with considerable industrial applicability in the light of the prior art, which is established in the following paragraphs.
ANALYSIS OF NOVELTY AND INVENTIVE STEP OF THE INVENTION
[047] The instant invention discloses a two-stepped flow process for the continuous production of 2-Chloro-1,1 dimethoxyethane comprising chlorination of vinyl acetate by Cl2 under pressure and at low-temp conditions followed by alcoholysis by methanol in a flow reactor. The novelty of the invention lies in the use of a continuous flow reactor for the manufacture of 2-chloro-1,1-dimethoxyethane in a two-stepped manner, wherein contact of chlorine employed in the chlorination step with methanol used in the transesterification reaction of the second step is avoided, with intermittent degassing of the reaction mixture to remove dissolved free chlorine gas that leads to considerable reduction in possibility of formation of explosive MeOCl and also by the use of a falling film evaporator (FFE).
[048] Inventive step lies in coming out with a continuous flow process for the continuous production of 2-chloro-1,1-dimethoxyethane by chlorination of vinyl acetate in step 1 followed by alcoholysis in step 2 of the product from step 1 using methanol, which improved the yields considerably. Further, the inventive step also lies in coming out with a process of manufacturing CADMA with minimal wastage of Cl2, solvents and neutralizing reagents making the entire process economical, safe, and environmentally friendly.
INDUSTRIAL APPLICABILITY OF THE INVENTION
[049] The instant invention discloses a two stepped flow process for the continuous production of 2-chloro-1,1-dimethoxyethane which finds extensive application in manufacturing industries as a drug-intermediate, precursor, intermediate in flavouring agents, and pesticides and possesses tremendous economic value which has to be exploited.
[050] Those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for designing other products without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the claims are not to be limited to the specific examples depicted herein. For example, the features of one example disclosed above can be used with the features of another example.
[051] Furthermore, various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept. For example, the geometric configurations disclosed herein may be altered depending upon the application, as may be the material selection for the components. Thus, the details of these components as set forth in the above-described examples, should not limit the scope of the claims.
[052] The exemplary embodiments of the instant invention can be realized with the help of the following examples.
Example 1
[053] 4 mL/minute of VAM is pumped into inhouse TRSM along with 300 to 340 mL of Chlorine gas at 2.3 barg pressure and 3 to 7 o C at the reactor jacket. The liquid residence time is 10minutes. The collected material after back pressure regulator is then passed through a film evaporator to remove excess chlorine and then collected into a receiver. Material collected is passed into TRSM at 1.6 ml/min and methanol at 3.05 ml/min and collected into a receiver at a temperature of 5 o C at the reactor jacket. The collected material is then passed into a CSTR at 9.2 mL/min along with methanolic ammonia at 5.67 ml/min at temperature of 10 to 15 oC. The pH is adjusted to 7 to 8. Organic layer is then subjected to distillation to remove methanol and methyl acetate. The reboiler material is then washed with aqueous ammonia to a pH of 9. Organic layer obtained after washing is distilled at 55 to 65 deg.C under vacuum of 550 to 650 mbar to get CADMA of purity > 99.5%. The obtained weight is found to be 74 % of theoretical yield based on assay.

Example 2
[054] 91 g of vinyl acetate is processed in a continuous mode by passing 4 mL/minute of VAM is into inhouse Tubular flow reactor with static mixers along with 300 to 340 mL of Chlorine gas at 2.5 barg pressure and 5 o C at the reactor jacket. The liquid residence time is 10minutes. The collected material after back pressure regulator is then passed through a film evaporator to remove excess chlorine and then collected into a receiver. Material collected is passed into inhouse flow reactor at 1.6 ml/min and methanol at 3.05 ml/min and collected into a receiver at a temperature of 5 o C at the reactor jacket. The collected material is then passed into a CSTR at 9.2 mL/min along with methanolic ammonia at 5.67 ml/min at temperature of 10 to 15 oC. The pH is adjusted to 7 to 8. Organic layer is then subjected to distillation to remove methanol and methyl acetate. The reboiler material is then washed with aqueous ammonia to a pH of 9. Organic layer obtained after washing is distilled at 55 to 65 deg.C under vacuum of 550 to 650 mbar to get CADMA of purity > 99.5%. The obtained weight is found to be 73 % of theoretical yield based on assay.
Example 3
[055] 5 mL/minute of VAM is pumped into AFR along with 600 to 650 mL of Chlorine gas at 2 to 4 barg pressure and -5 o C at the reactor jacket. The liquid residence time is 1.6 minutes. The collected material after back pressure regulator is then passed through a condenser to remove excess chlorine and then collected into a receiver. Material collected is passed into inhouse flow reactor at 1.6 ml/min and methanol at 3.05 ml/min and collected into a receiver at a temperature of -5 o C at the reactor jacket. The collected material is then passed into a CSTR at 9.2 mL/min along with methanolic ammonia at 5.67 ml/min at temperature of 10 to 15 oC. The pH is adjusted to 10 to 12. The salt is then filtered, and filter mother liquor is then subjected to distillation at vapour temperature of 32 to 40 deg. C under vacuum.
, Claims:I/We Claim:
1. A two-stepped continuous flow process for preparing dialkyl substituted haloacetals, or compounds of the structure (I)
Wherein, X is a halogen; R and R are similar lower alkyl groups;
(I)

in a flow-reactor comprising step (1) of passing elemental halogen under pressure into an alkenyl ester containing at least one vinyl linkage followed by step (2) of alcoholysis of the halogenated alkenyl ester with a lower alcohol wherein, step (1) comprises of:
(a) passing of elemental halogen into a flow reactor under pressure into an alkenyl ester alone without any solvent wherein the pressure in the reactor is maintained by a back pressure regulator and (b) collecting the resulting 1, 2 dihaloalkyl ester into a collection receiver through a gas separator or Falling film evaporator under anhydrous conditions,
Step (2) comprises of:
(c) alcoholysis and transesterification of the 1, 2-dihaloalkyl ester from step (1) with a lower alcohol under pressure to form the product of structure (I) and ester of the lower alcohol containing at least one -OH group in its structure used for alcoholysis along with the hydrogen halide and water as by-products of the reaction and (d) neutralization of the reaction mass obtained from ( c) after with ammonia at 10 to 20 oC.
2. The alkenyl ester as claimed in claim 1 is selected preferably from a group comprising vinyl ester, substituted vinyl ester, cycloalkenyl ester, heteroalkenyl ester, arylalkenyl ester, substituted alkenyl ester and more particularly from vinyl esters.
3.The alkenyl ester as claimed in claim 1 is preferably vinyl acetate.
4. The elemental halogen as claimed in claim 1 is selected from a group comprising Cl2, Br2, I2, F2.
5. The elemental halogen as claimed in claim 1 is preferably Cl2 gas.
6. The passing of elemental halogen, preferably Cl2 into alkenyl ester under pressure of step (1) as claimed in claim 1 is preferably done anywhere between 0 to 5 barg.
7. The passing of elemental halogen into alkenyl ester of step (1) as claimed in claim 1 is preferably done at -10 to 60 oC.
8. The alcoholysis and transesterification of the 1,2-dihaloalkyl ester of step (2) as claimed in claim 1 is done with a lower alcohol wherein the lower alcohol is selected from a group comprising of methanol, ethanol, isopropanol, n-propanol, ethylene glycol, cyclohexanol, 2-butanol, 2-amyl alcohol, allyl alcohol and methallyl alcohol.

9. The alcoholysis and transesterification of the 1,2-dihaloalkyl ester of step (2) with a lower alcohol as claimed in claim 1 is done more preferably with methanol at -10 to 60 oC.
10. The flow process as claimed in claim 1 comprises neutralization (d) of step (2) accomplished by ammonia wherein ammonia is selected from a group comprising of aqueous ammonia, methanolic ammonia, gaseous ammonia, anhydrous ammonia.
11. The flow process as claimed in claim 1 comprises neutralization (d) of step (2) wherein, methanolic ammonia is preferably used to obtain a pH range of 7-12.
12. The flow process for the continuous production of compounds of structure (I) as claimed in claim1 yields 2-Chloro-1,1-dimethoxyethane when vinyl acetate, elemental Cl2 and methanol are preferably used.
13. The flow process as claimed in claim 1 is carried out in a flow reactor selected from a group comprising continuous flow reactor, tubular reactor with static mixers, Corning-Advanced flow reactor, static element mixer followed by flow reactor, agitated cell reactor, screw reactor, agitated reactor, tubular reactor followed by continuous stirred tank reactor and combinations thereof.