Description:FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

“PROCESS FOR PREPARATION OF POLYHALOCARBOXYLIC ACID CHLORIDES”
The present application is an improvement over the invention claimed in the complete specifications of the main patent application IN202211062441 filed on 02-11-2022.

SRF LIMITED, AN INDIAN COMPANY,
SECTOR 45, BLOCK-C, UNICREST BUILDING,
GURGAON – 122003,
HARYANA (INDIA)

The following specification particular describes the invention and manner in which it is to be performed.

FIELD OF THE INVENTION
The present invention relates to a process for preparation of a polyhalocarboxylic acid chloride of formula (I) R1-C(O)Cl, by the reaction of polyhaloalkanes of formula (II) R1-CHCl2 with oxygen in the presence of radical initiator, wherein R1 is a fluorinated and/or chlorinated C1-C3 alkyl.

BACKGROUND OF THE INVENTION
The polyhalocarboxylic acid chlorides are important intermediates and reagents that find application in various chemical industries including pharmaceutical and agriculture.
Various methods are known in the literature for the preparation of acid chlorides.
United States Patent No. 5241113 discloses a process for preparation of trifluoroacetyl chloride by reacting 1,1-dichloro-2,2,2-trifluoroethane with molescular oxygen over a carbon bed.
United States Patent No. 5545298 discloses a process for preparation of polyfluorochlorocarboxylic acid chlorides and perfluorocarboxylic acid chlorides by photochemical oxidation of corresponding alkanes.
Indian Patent No. 290252 filed by the same applicant discloses a process for preparation of trifluoroacetyl chloride comprising reacting trifluoroacetyl fluoride with a chlorinated acetyl chloride selected from a group of selected monochloroacetyl chloride, dichloroacetyl chloride and trichloroacetyl chloride, preferably trichloroacetyl chloride.
IN202211062441 filed by the same applicant discloses an effluent free process for preparation of polyhalocarboxylic acid chlorides by reacting polyhalocarboxylic acid with phosphorus trichloride and chlorine.
Chinese Application No. 101735033 discloses a process for preparation of trifluoroacetyl chloride from 2,2-dichloro-1,1,1-trifluoroethane by reacting CFC-123 with oxygen and chlorine using mercury lamp radiation.
United States Patent No. 3883407 discloses a process for preparation of trifluoroacetyl chloride from 2,2-dichloro-1,1,1-trifluoroethane by reacting CFC-123 with oxygen at 120 psig under UV irradiation using 2000 W UV lamp.
The above processes are less suitable at commercial scale and results in the low selectivity thereby leads to the formation of impurities and considerable loss of yield.
It has been now found by the present applicant that using a specific reaction conditions can help to improve the selectivity towards the product. The inventors of the present invention have come up with a facile, time-saving, energy efficient, environmental friendly process for preparation of polyhalocarboxylic acid chlorides.

OBJECTIVE OF THE INVENTION
An object of the present invention is to provide an environment friendly and commercially viable process for preparation of a polyhalocarboxylic acid chloride of formula (I) R1-C(O)Cl, wherein R1 is a fluorinated and/or chlorinated C1-C3 alkyl by vapour phase oxidation of polyhaloalkanes of formula (II) R1-CHCl2 with oxygen and radical initiator in the presence of UV radiation.

SUMMARY OF THE INVENTION
The present invention provides an improved process for preparation of polyhalocarboxylic acid chloride of formula (I), comprising the steps;
R1-C(O)Cl
Formula I
wherein R1 is a fluorinated and/or chlorinated C1-C3 alkyl;
a) oxidising the preheated polyhaloalkanes of formula (II) with oxygen and a radical initiator to form a gaseous mixture;
R1-CHCl2
Formula II
wherein R1 is as defined above,
b) irradiating the gaseous mixture of step a) in FEP/PFA coil using radiating source to obtain polyhalocarboxylic acid chloride, having selectivity >99%.

DETAILED DESCRIPTION OF DRAWING
Figure 1 refers to the continuous flow reactor system of vapor-vapor phase photo chemical reaction consists of CY-1 represent as oxygen cylinder; CY-2 represent as polyhaloalkanes cylinder; CY-3 represent as radical initiators cylinder; R-1 represent as UV reactor (includes quartz jacket of UV reactor and PFA/FEP coil); C1 represent as condenser; R2 represent as collection reactor and V1 & V2 represent as Vent valves. A preheated gaseous mixture of polyhaloalkanes, oxygen, and radical initiators was charged into coil (FEP/PFA), which is connected with quartz part of UV reactor and simultaneously irradiated by UV lamp. After irradiation, resultant gaseous mixture enter into the condenser and then collected the crude product in the collection reactor.

DETAILED DESCRIPTION OF THE INVENTION
In an embodiment, the present invention provide an improved process for preparation of a polyhalocarboxylic acid chloride of formula (I) R1-C(O)Cl, wherein R1 is a fluorinated and/or chlorinated C1-C3 alkyl by vapour phase oxidation of polyhaloalkanes of formula (II) R1-CHCl2 with oxygen and radical initiator.
As used herein, “radical initiator” selected from a group consisting of bromine, chlorine and tert-butyl peroxy-2-ethyl hexanoate or a like.
As used herein, the radiating source in the present invention emits light in the range of 200 to 400 nm.
As used herein, the FEP/PFA coil refers to fluorinated ethylene-propylene or perfluoroalkoxy coil.
In an embodiment, the radiating source used in the present invention is selected from light bulbs, light emitting diodes (LEDs), halogen lamps or fluorescent lamps or fluorescent tubes, discharge lamps, quartz-mercury lamp (doped mercury lamps), high pressure mercury vapour lamp, medium-pressure mercury-vapor lamps (UV lamp), using a 500W Mazda lamp, and tungsten incandescent bulb can be used as light source.
In an embodiment, a preheated gaseous mixture of polyhaloalkanes, oxygen and radical initiator may be radiated with a wavelength in the range of 200 to 400 nm.
In a preferred embodiment, the irradiation may be carried out at a wavelength in the range of 280-350 nm.
As used herein, the term “fluorinated and/or chlorinated C1-C3 alkyl” refers to trifluoromethyl, difluoromethyl, trifluoroethyl and chlorotetrafluoroethyl or the like.
As used herein, the term “a carboxylic acid chloride of formula (I) R1-C(O)Cl” includes acid chlorides selected from a group consisting of trifluoroacetyl chloride, difluoroacetyl chloride, trifluoropropionic acid chloride and chloro tetrafluoro propionic acid chloride or the like.
As used herein, the term “polyhaloalkanes” includes the alkanes selected from a group consisting of 2,2-dichloro-1,1,1-trifluoroethane (R-123), 2,2-dichloro-1,1-difluoroethane, 3,3-dichloro-1,1,1-trifluoropropane and 1,3,3-trichloro-1,1,2,2-tetrafluoro propane or the like.
In another embodiment, the present invention provides a process for preparation of polyhalocarboxylic acid chlorides by vapour phase oxidation of polyhaloalkanes with oxygen and radical initiator under atmospheric pressure.
In an embodiment, the process of present invention is carried out in a continuous mode, wherein reactants are continuously supplied, and product is continuously isolated.
In another embodiment, the irradiation is carried out at temperature in the range of 30°C to 200°C. In a preferred embodiment, the irradiation is carried out at temperature in the range of 30°C to 150°C.
In another embodiment, the process of the present invention is irradiated by UV lamp in range of 70 - 450W, preferably 125 W.
In another embodiment of the present invention, the irradiation is carried out without using any solvent.
In an embodiment, the moles ratio of polyhaloalkanes, oxygen and radical initiator is used in the range of 1: 0.8-3.0 : 0.1-0.5 moles, preferably in the range of 1.0 : 1.0 : 0.3 moles.
In another embodiment, the unreacted polyhaloalkane is recovered and recycled from the reaction process.
The recovery % of polyhaloalkane is greater than 50%. This helps in eliminating generation of waste and provides economical process.
In another embodiment, the invention involves passing polyhaloalkane and oxygen at a rate of 0.007 : 2 to 0.5 : 100 ml/min, preferably at a rate of 0.06 : 15 ml/min.
The process of the present invention is carried out in a continuous mode or a batch mode, preferably in a continuous mode.
In continuous mode, preheated gaseous mixture at 180? of polyhaloalkane, oxygen and radical initiator is continuously charged into FEP/ PFA coil in a vapor phase, coil is wrapped as coil on quartz jacket and fitted with photo chemical reactor and simultaneously irradiated by using UV lamp. Importantly, the rate of polyhaloalkane and oxygen introduce into the reactor is adjusted to avoid more condensation of polyhaloalkanes.
In an embodiment, the present invention provides a process for preparation of polyhalocarboxylic acid chlorides, wherein polyhaloalkanes and oxygen are effectively added in a reactor to avoid any hazels and to provide better results.
In an embodiment, the present invention provides a process for preparation of polyhalocarboxylic acid chlorides by vapour phase oxidation of polyhaloalkanes using FEP tube reactors.
In another embodiment, the present invention provides a process for preparation of polyhalocarboxylic acid chlorides by vapour phase oxidation of polyhaloalkanes using PFA tube reactors.
In an embodiment, process for preparation of polyhalocarboxylic acid chloride of formula (I) R1-C(O)Cl in a continuous flow reactor using FEP coil is wrapped as coil on quartz jacket and fitted with photochemical reactor by vapor phase oxidation under UV irradiation. A preheated (180?) gaseous mixture of polyhaloalkane compound of formula (II), oxygen and radical initiator was charged into FEP coil and simultaneously was irradiated by using 125 W UV lamp. Importantly, a rate of polyhaloalkanes and oxygen were adjusted to avoid more condensation of compound of formula (II) to get maximum conversion of it and get selectivity >99%.
In another embodiment, process for preparation of polyhalocarboxylic acid in a continuous flow using PFA tube is wrapped as coil on quartz jacket and fitted with photochemical reactor by vapor phase oxidation under UV irradiation. Preheated gaseous mixture of polyhaloalkane, oxygen and initiator was charged into PFA coil and simultaneously was irradiated by using 450W UV lamp.
In an embodiment, process for preparation of polyhalocarboxylic acid chloride in a continuous flow using either FEP tube is wrapped as coil on quartz jacket and fitted with photochemical reactor by vapor phase oxidation under UV irradiation. preheated gaseous mixture of (170?) polyhaloalkanes, oxygen and initiator was charged into PFA coil and simultaneously was irradiated by using 70 W UV lamp.
The present invention for preparation of polyhalocarboxylic acid chlorides have following advantages over the known methods:
1. The present invention involves the use of specific power range (70-450 W), more preferably 125 W) of UV lamps, that range prevents the use of highly expensive equipment, and thereby the overall cost of the process reduces.
2. The mode of addition of reactant and reagent used in the reaction positively affects the product selectivity. The present inventors observed an improvement in the selectivity with adjustable amount of addition of polyhaloalkanes and oxygen to the reaction procedure.
3. The present invention involves the use of FEB/PFA tube reactors which helps in encapsulating the UV emitting source. Additionally, using such type of reactor in the process helps in improving reaction strength and also helps to avoid the corrosion of the reactor.
4. The process of the present invention provides efficient recycling and recovery of key reagents.
5. The process of the present invention provides an efficient and environmental friendly process for the preparation of polyhalocarboxylic acid chlorides.
The completion of the reaction may be monitored by any one of chromatographic techniques such as thin layer chromatography (TLC), high pressure liquid chromatography (HPLC), ultra-pressure liquid chromatography (UPLC), Gas chromatography (GC), liquid chromatography (LC), Ionic chromatography (IC) and alike or acid-base titration.
Embodiments of the invention are not mutually exclusive but may be implemented in various combinations. The described embodiments of the invention and the disclosed examples are given for the purpose of illustration rather than limitation of the invention as set forth in the appended claims.
The following example is given by way of illustration and therefore should not be construed to limit the scope of the present invention.

EXAMPLES
Example 1: Preparation of trifluoroacetyl chloride
A preheated (180?) gaseous mixture of 2,2-dichloro-1,1,1-trifluoroethane (34 g, 0.22 moles), oxygen (7.07 g, 0.22 moles) and chlorine (4 g, 0.057 moles) was charged into FEP coil reactor with a specific flow rate (ml/minute) of 0.06 : 13 : 0.003 (R-123 : O2 : Cl2) and simultaneously irradiated by using 125 W UV lamp at 150 oC and get conversion of R-123 50%.
Selectivity >98.5%.
Example 2: Preparation of trifluoroacetyl chloride
A preheated (180?) gaseous mixture of 2,2-dichloro-1,1,1-trifluoroethane (34 g, 0.22 moles), oxygen (7.07 g, 0.22 moles) and chlorine (4 g, 0.057 moles) was charged into FEP coil reactor with a specific flow rate (ml/minute) of 0.06 : 13 : 0.003 (R-123 : O2 : Cl2) and simultaneously irradiated by using 125 W UV lamp at 150 oC and get conversion of R-123 60% and selectivity >99%.
Example 3: Preparation of trifluoroacetyl chloride
A preheated (170?) gaseous mixture of 2,2-dichloro-1,1,1-trifluoroethane (30 g, 0.20 moles), oxygen (6.13 g, 0.19 moles) and chlorine (3 g, 0.042 moles) was charged into PFA coil with a specific flow rate (ml/minute) of 0.06 : 13 : 0.003 (R-123 : O2 : Cl2) and simultaneously irradiated by using 450 W UV lamp at 90oC and get the conversion of 2,2-dichloro-1,1,1-trifluoroethane 70% and selectivity >99%.
Example 4: Preparation of trifluoroacetyl chloride
A preheated (170?) gaseous mixture of 2,2-dichloro-1,1,1-trifluoroethane (26 g, 0.17 moles), oxygen (8.57 g, 0.27 moles) and chlorine (5 g, 0.07 moles) was charged into PFA coil with a specific flow rate (ml/minute) of 0.06 : 20 : 0.005 (R-123 : O2 : Cl2) and simultaneously irradiated by using 70 W UV lamp at 60 oC and get conversion of R-123 45% and selectivity >99%.
Example 5: Preparation of trifluoroacetyl chloride
A preheated (180?) gaseous mixture of 2,2-dichloro-1,1,1-trifluoroethane (30 g, 0.20 moles), oxygen (6.20 g, 0.19 moles) and bromine (1.5 g, 0.01 moles) was charged into FEP coil reactor with a specific flow rate (ml/minute) of 0.06 : 13 : 0.001 (R-123 : O2 : Br2) and simultaneously irradiated by using 450W UV lamp at 150 oC and get conversion of R-123 62% and selectivity >98.5%.
Example 6: Preparation of trifluoroacetyl chloride
A preheated (170?) gaseous mixture of 2,2-dichloro-1,1,1-trifluoroethane (20 g, 0.13 moles) and oxygen (4.0 g, 0.12 moles) was charged into PFA coil (filled by tert-butyl peroxy-2-ethyl hexanoate (2.5 g, 0.01 moles)) with a specific flow rate (ml/minute) of 0.06 : 13 (R-123 : O2) and simultaneously irradiated by using 450 W UV lamp at 70oC and get the conversion of 2,2-dichloro-1,1,1-trifluoroethane 57% and selectivity >98%.
Example 7: Preparation of difluoroacetyl chloride
A preheated (180?) gaseous mixture of 1,1-dichloro-2,2-difluoroethane (30 g, 0.22 moles), oxygen (10.66 g, 0.33 moles) and chlorine (4 g, 0.057 moles) was charged into FEP coil reactor with a specific flow rate (ml/minute) of 0.05 : 19 : 0.003 ( 1,1-dichloro-2,2-difluoroethane: O2 : Cl2) and simultaneously irradiated by using 125 W UV lamp at 90 oC and get conversion of 1,1-dichloro-2,2-difluoroethane 60%.
Selectivity >97%.

Example 8: Preparation of chlorotetrafluoro propionylchloride
A preheated (180?) gaseous mixture of 1,1,3-trichloro-2,2,3,3-tetrafluoropropane (25 g, 0.11 moles), oxygen (3.98 g, 0.12 moles) and chlorine (3 g, 0.042 moles) was charged into PFA coil reactor with a specific flow rate (ml/minute) of 0.12 : 19 : 0.006 ( 1,1,3-trichloro-2,2,3,3-tetrafluoropropane: O2 : Cl2) and simultaneously irradiated by using 125 W UV lamp at 150oC and get conversion of 1,1,3-trichloro-2,2,3,3-tetrafluoropropane 55%.
Selectivity >98%.
Example 9: Preparation of chlorotetrafluoro propionylchloride
A preheated (180?) gaseous mixture of 1,1,3-trichloro-2,2,3,3-tetrafluoropropane (25 g, 0.11 moles), oxygen (5 g, 0.16 moles) and bromine (4 g, 0.025 moles) was charged into PFA coil reactor with a specific flow rate (ml/minute) of 0.09 : 19 : 0.007 ( 1,1,3-trichloro-2,2,3,3-tetrafluoropropane: O2 : Br2) and simultaneously irradiated by using 450 W UV lamp at 150 oC and get conversion of 1,1,3-trichloro-2,2,3,3-tetrafluoropropane 62%.
Selectivity >96.5%.

SRF LIMITED NO. OF SHEETS: 1
APPLICATION NO. SHEET No. 1 OF 1

Figure-1

, Claims:WE CLAIM
1. An improved process for preparation of polyhalocarboxylic acid chloride of formula (I), comprising the steps;
R1-C(O)Cl
Formula I
wherein R1 is a fluorinated and/or chlorinated C1-C3 alkyl;
a) oxidizing the preheated polyhaloalkanes of formula (II) with oxygen and a radical initiator to form a gaseous mixture;
R1-CHCl2
Formula II
wherein R1 is as defined above,
b) irradiating the gaseous mixture of step a) in FEP/PFA coil using radiating source to obtain polyhalocarboxylic acid chloride, having selectivity >99%.
2. The process as claimed in claim 1, wherein the radiating source is selected from light bulbs, light emitting diodes (LEDs), halogen lamps or fluorescent lamps or fluorescent tubes, discharge lamps, quartz-mercury lamp (doped mercury lamps), high pressure mercury vapour lamp, medium-pressure mercury-vapor lamps (UV lamp), mazda lamp and tungsten incandescent bulb.
3. The process as claimed in claim 1, wherein the radiating source emits light in the range of 200 to 400 nm.
4. The process as claimed in claim 1, wherein the irradiation is carried out under atmospheric pressure.
5. The process as claimed in claim 1, wherein the radical initiator is selected from a group consisting of bromine, chlorine and tert-butyl peroxy-2-ethyl hexanoate.
6. The process as claimed in claim 1, wherein the irradiation is carried out in a continuous mode.
7. The process as claimed in claim 1, wherein the irradiation is carried out at temperature in the range of 30°C to 200°C.
8. The process as claimed in claim 1, wherein the irradiation is carried out in absence of a solvent.
9. The process as claimed in claim 1, wherein the moles ratio of polyhaloalkanes, oxygen and radical initiator used is in the range of 1: 0.8-3.0 : 0.1-0.5 moles.
10. The process as claimed in claim 1, wherein the unreacted polyhaloalkane is recovered and recycled from the reaction process.

Dated this 27th day of September 2023.