DESC:
FORM 2
THE PATENT ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:

“PROCESS FOR THESYNTHESIS OF DIIODOPERFLUOROALKANES”

2.APPLICANT(S):
Name Nationality Address
GUJARAT FLUOROCHEMICALS LIMITED INDIAN INOX Towers, 17, Sector -16A, Noida, Uttar Pradesh 201 301, India


3. PREAMBLE TO THE DESCRIPTION:

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

FIELD OF THE INVENTION
The present invention pertains to a process for the synthesis of diiodoperfluoroalkanes. More particularly, the present invention relates to a process for the synthesis of diiodoperfluoroalkanes, wherein the process comprises reacting iodine, and gaseous tetrafluoroethylene (TFE) optionally using a catalyst at a temperature ranging between 150-200oC and time duration ranging between 5-15 hours to isolate the reaction product, which is further subjected to fractional distillation for isolating the individual fractions of diiodoperfluoroalkanes viz, 1,2-diiodotetrafluoroethane (C2DI), 1,4-diiodooctafluorobutane (C4DI), 1,6-diiodoperfluorohexane (C6DI); and 1,8-diiodoperfluorooctane (C8DI) having Gas Chromatography (GC) purity of individual fractions not less than 98%.

BACKGROUND OF THE INVENTION
Diiodoperfluoroalkanes represented by the formula I-(CF2-CF2)n-I, wherein n= 1 to 6 are chemical compounds having a wide range of industrial applications. They are important building blocks that can be used for synthesizing a variety of fluorinated compounds and pharmaceuticals. The compounds such as 1,4-diiodooctafluorobutane (C4DI) and 1,6-diiodoperfluorohexane (C6DI) are being used as chain transfer agents in polymerization reactions.

EP1422211B1 discloses that diiodoperfluoroalkanes are generally synthesized by reacting tetrafluoroethylene (TFE) with iodine or 1,2-diiodoperfluoroethane, however, said process is required to be carried out at high reaction temperature (> 240° C) and pressure (> 3.1 MPa) to achieve reasonable yields and conversion. Also, since TFE is highly reactive, its flammability and explosivity is known to increase with increasing temperature and pressure, hence, handling of TFE at such high temperature becomes rather difficult. Further, 1,2-diiodoperfluoroethane that is used as the starting material is highly toxic in nature.

Telomerization processes comprising the reaction of tetrafluoroethylene (TFE) with iodine or 1,2-diiodoperfluoroethane are also known in the art, however, said processes are known to be associated with either poor yield and low conversion rates or high temperature and pressure conditions. Furthermore, a large amount of excessive tetrafluoroethylene gas needs to be added, the reaction pressure remains high, the reaction time is long, the exothermic reaction is strong, and the risk is high. In addition, in the reaction process of the closed system, a part of tetrafluoroethylene gas is dimerized into octafluorocyclobutane to exist in the reaction system, the octafluorocyclobutane is a free radical trapping agent, and the increase of the octafluorocyclobutane accumulated along with the reaction in the reaction system can cause the reaction rate to be reduced, even the reaction is terminated, so that the tetrafluoroethylene gas in the kettle needs to be replaced once again to continue the reaction after the telomerization reaction is carried out for a certain time, and the industrial application prospect of the telomerization reaction is undoubtedly influenced by the reaction mode; in addition, the existing telomerization reaction reports are basically batch kettle type reactions, the operation is complicated, and the reaction efficiency is low.

In GB Patent No. GB1301617A, it discloses a process for preparing alpha-omegadiiodoper-fluoroalkanes by reacting 1,2-diiodotetra-fluoroethane as the starting material with 4.25 times of tetrafluoroethylene at 300-1500oC and 650psi (45.6995 kg/cm2) for more than 26 hours under the catalysis of benzoyl peroxide to obtain a mixture of perfluoroalkyl diiodides followed by telomerization, wherein I(C)2(F)4)nI. The content of nI (n =1, 2, 3, 4) was 62.9%,17.6%, 11.5%,2.5%, 35% of the conversion of 1, 2-diiodoethane, respectively.

The disclosures of JPS6131084B2 provides that thermal decomposition of 1,2-diiodoperfluoroethane in presence of iodine can also be used for the manufacture of 1,4-diiodoperfluorobutane and higher order diiodoperfluoroalkanes, however, the process has low conversion rate and requires separation of the product from a large amount of iodine.

In view of the above disclosures and to overcome the prior-art problems, it is pertinent to note that there exists an inherent need in the art to develop a safe and efficient process for the synthesis of diiodoperfluoroalkanes that provides a high conversion rate and yield and that can be carried out at comparatively milder conditions of temperature and pressure. Also, the process should be such that it should minimizes the use of any hazardous reagent or its way for safely handling for scaling up purposes. Accordingly, the inventors of the invention have developed an improved process for the preparation of diiodoperfluoroalkanes that solves the above-mentioned problems besides cost efficient, safe and amenable to scaleup for commercial production with consistent quality.

OBJECTIVES OF THE INVENTION
In one objective of the present invention is to provide a safe and cost efficient, environment-friendly process for the synthesis of diiodoperfluoroalkanes using tetrafluoroethylene and iodine.

In another objective of the present invention is to provide a safe process for the synthesis of diiodoperfluoroalkanes at significantly lower temperature and pressure conditions besides lesser time duration for efficient conversion.

It is yet another objective of the present invention to provide a process for the synthesis of diiodoperfluoroalkanes with increased yield, high purity (GC) and reaction rate.

SUMMARY OF THE INVENTION
The present invention relates to a process for the synthesis of diiodoperfluoroalkanes using tetrafluoroethylene (TFE) and iodine at significantly lower temperature and pressure conditions besides lesser time duration for efficient conversion.

In one of the aspect of the present invention, it relates to a process for synthesizing diiodoperfluoroalkanes comprising the steps of:
a) introducing iodine in the reactor followed by optionally adding catalyst
b) performing the nitrogen purging to reduce the oxygen content to less than 20 ppm
c) add tetrafluoroethylene (TFE) into a reaction vessel;
d) heating the reaction mixture under stirring at temperature ranging between 150- 200°C and time duration ranging between 5-15 hours;
e) cooling the reaction mixture to temperature ranging between 20- 30°C;
f) recovering the diiodoperfluoroalkanes as reaction product.

In another aspect according to the present invention, it relates to a process of recovering the diiodoperfluoroalkanes as the reaction product of step f), further comprising the steps of –
a. optionally filtering the reaction product after reaction completion
b. washing the step a) reaction product
c. collecting the organic layer and performing the fractional distillation
d. isolating the individual pure fractions of 1,2-diiodotetrafluoroethane (C2DI), 1,4-diiodooctafluorobutane(C4DI); 1,6-diiodoperfluorohexane(C6DI); and 1,8- diiodoperfluorooctane (C8DI)

BRIEF DESCRIPTION OF DRAWINGS
Figure 1: is an illustration of purity of C2DI by Gas Chromatography as prominent single peak in accordance with the present invention.

Figure 2: is an illustration of purity of C4DI by Gas Chromatography as prominent single peak in accordance with the present invention.

Figure 3: is an illustration of purity of C6DI by Gas Chromatography as prominent single peak in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION
Discussed below are some representative embodiments of the present invention, wherein the invention in all its aspects are not construed to be limited to the specific details and representative methods.

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

It is to be noted that, as used in the specification, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "‘or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The methods, devices, and examples provided herein are illustrative only and not intended to be limiting.

The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

Groupings of alternative elements or embodiments of the invention disclosed herein may not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims. Embodiments of the present invention will be described herein below in detail.

In one embodiment according to the present invention, it provides a process for synthesizing diiodoperfluoroalkanes comprising the steps of:
a) introducing iodine in the reactor followed by optionally adding catalyst
b) performing the nitrogen purging to reduce the oxygen content to less than 20 ppm
c) add tetrafluoroethylene (TFE) into a reaction vessel;
d) heating the reaction mixture under stirring at temperature ranging between 150- 200°C and time duration ranging between 5-15 hours;
e) cooling the reaction mixture to temperature ranging between 20- 30°C;
f) recovering the diiodoperfluoroalkanes as reaction product

According to present invention of a process for synthesizing diiodoperfluoroalkanes, wherein the step a) of the present embodiments, it provides introducing iodine in the reactor. The iodine may be used in the solid crystalline or powder form and may be added directly or in the solution form with a suitable solvent.

The reaction may be carried out without catalyst, however, catalyst may use optionally to perform the reaction either to enhance the quality or speed of reaction or control the reaction kinetics to safeguard overall course of reaction.

The catalysts if used optionally, may be selected from copper or copper iodide or copper chloride or copper bromide or combinations thereof.

In a particular embodiment, inventors have used Copper powder as an optional catalyst, however, in another particular example, the reaction was performed without catalyst also.

The overall difference observed by scientist of present invention was merely the time difference though one of the fractions of C4DI and C6DI has enhanced which resulted in the recovery for high output for this fraction in case of using Copper powder as catalyst.

In the step b) of the present embodiments, it provides performing the nitrogen purging to reduce the oxygen content to less than 20 ppm. Inventors of the present application have surprisingly observed that presence of oxygen for this reaction may be lethal to its productivity and quality. Hence, this is an essential step in order to avoid side chain or oxidative impurities formation from the reaction initiation onwards. An excess amount of oxygen was found to create the composition of diiodoperfluoroalkanes with poor yields of fractions and large number of impurities formation leading the process to be non-viable for scaleup and commercial production yielding in consistently the poor quality of fractions. The oxygen content of the reactor was analyzed and measure using AMI (Advanced Micro Instruments Inc.) model – 1000RS wherein the detection range of the said O2 analyzer ranges from 0 – 1000 ppm.

In step c) of the present embodiments, it provides addition of tetrafluoroethylene (TFE) into the reactor. The tetrafluoroethylene (TFE) may be used is in gaseous form at 15-25 kg/cm2 is added when the temperature of the reactor reached at 150-190 oC and the pressure comes down to below 10 kg/cm2, TFE was added while maintaining the pressure of 15-25 kg/cm2.

In step d) of the present embodiments, it provides heating the reaction mixture under stirring at temperature ranging between 150-200 oC and for time duration ranging between 5-15 hours to maintain the pressure and temperature of the reactor, which is essential for the present invention.

In a particular embodiment, the heating of reaction mixture under stirring at temperature ranging between 180-190 oC and for time duration ranging between 10-12 hours while maintaining the pressure ranging between 18-20 kg/cm2

In step e) of the present embodiments, it provides cooling the reaction mixture to temperature ranging between 20-30oC, which will crystalline the reaction mixture providing the reaction product.

In step f) of the present embodiments, it provides recovering the diiodoperfluoroalkanes as reaction product, wherein the conventional steps of filtering and washing are followed to recover the reaction end product, which is subjected to fractional distillation.

In another embodiment according to the present invention, it provides a unique process for recovering the reaction product diiodoperfluoroalkanes comprising the steps of –
a. Optionally filtering the reaction product containing a composition of diiodoperfluoroalkanes
b. washing the step a) reaction product
c. collecting the organic layer and performing the fractional distillation
d. isolating the individual fractions of 1,2-diiodotetrafluoroethane (C2DI), 1,4-diiodooctafluorobutane (C4DI); 1,6-diiodoperfluorohexane (C6DI); and 1,8- diiodoperfluorooctane (C8DI)

In step a) of the present embodiments, it provides filtering the reaction product containing the mixtures of diiodoperfluoroalkanes. This process provides the reaction product in improved quality characteristic usable for next stages. The filtering process may utilize conventional filters viz, candy or Whatman filter paper for small scale or membrane filter or Nutsche filter or carbon powder or granular carbon bed filter or the like. The obtained reaction filtered product is subjected for GC analysis for evaluating the composition of individual fractions.

In a particular embodiment, inventors of the present application have observed fractions GC analysis as –
EXAMPLE No C2DI C4DI C6DI C8DI
EXAMPLE 1 23% 37% 23% 9%
EXAMPLE 2 23% 39% 22% 6%
EXAMPLE 3 11% 42% 35% 6%
EXAMPLE 4 15% 41% 32% 7%
EXAMPLE 5 14% 40% 32% 7%
EXAMPLE 6 12% 35% 32% 7%

Inventors have also developed the aforementioned process, which may be optimized to enhance one of the desired fractions of either C2DI or C4DI or C6DI or C8DI as per need using variable conditions of temperature and/or catalyst along with feed control of TFE and Iodine.

In step b) of the present embodiments, it provides washing the step a) reaction product using aqueous solution of sodium thiosulphate. Preferably the washing is performed using 5-15% w/w aqueous solution of sodium thiosulphate.

In a particular embodiment, inventors of the present application have utilized about 10% w/w aqueous solution of sodium thiosulphate.

For washing purposes, other alternatives as chemical entity but are not limited to potassium thiosulfate or ascorbic acid or magnesium sulfate or magnesium chloride may be utilized.

In step c) of the present embodiments, it provides collecting the organic layer and performing fractional distillation. The fractional distillation is performed with the following fractional distillation parameters as:
Distillation Column: One-meter Glass bead column
Temperature & vacuum: 47-49°C/35 mmHg for C2DI
63-65°C/35 mmHg for C4DI
72-75°C/10 mmHg for C6DI

In step d) of the present embodiments, it provides isolating the individual fractions of 1,2-diiodotetrafluoroethane (C2DI), 1,4-diiodooctafluorobutane (C4DI); 1,6-diiodoperfluorohexane (C6DI); and 1,8- diiodoperfluorooctane (C8DI).

The reaction products obtained in step d) of the present embodiments, it provides GC purity of individual fractions not less than 98% and the Gas chromatography conditions for the analysis were as below:
GC Model: Agilent 8890
Column: DB 624 (30 m X 0.53 mm X 3 µm)
Program: 50 °C 2 min Hold
5 150 °C 0 min Hold
15 240 °C 10 min Hold (Total Run Time: 38 min.)
Flow Rate: 11.51 ml/min.

In yet another embodiments of the present invention, it provides TFE added in a molar ratio ranging from 2.0 to 15 with respect to 1 mole of iodine.
In yet another embodiments of the present invention, it provides the diiodoperfluoroalkanes which may be extracted using a solvent selected from the group consisting of chlorinated solvents, hydrocarbon solvents, and fluorinated solvents suitably to recover selectively a particular diiodoperfluoroalkanes.

The terms used for clarity are described herein below.
Catalyst
The term “catalyst” refers to a substance that is added to a reaction to increase the rate of the reaction or reduce the temperature or pressure of the reaction, without itself being consumed in the process. Catalysts not only provide for faster, energy efficient reactions but also provide selectivity to a reaction. The present invention has an optionally use of catalyst wherein the catalyst is selected from copper or copper iodide or copper chloride or copper bromide.

Reaction conditions
The iodine and TFE are reacted at a temperature of 150-200 °C. The temperature of the reaction may vary, for example, from 170-200 °C. In a preferred embodiment, the reaction is carried out at a temperature in the range of 180 to 190 °C.

The pressure of the reactor may vary from 8-25 kg/cm2. In a preferred embodiment, the reaction is carried out at a pressure in the range of 18-20 kg/cm2.

In a preferred embodiment, Iodine and optionally adding catalyst are introduced into a reaction vessel. First, nitrogen vacuum cycles are applied to the reactor to eliminate oxygen from the reactor. The nitrogen vacuum cycles are repeated until the oxygen concentration in the reactor reduces to less than 20 ppm. Once the desired oxygen concentration is achieved; the reactor is charged with 15-20 kg/cm2 TFE. The reactor is then heated to a temperature of 180-190°C. As the reactor is heated; the pressure of the reactor drops. Once the pressure is found to drop below 10 kg/cm2; further amount of TFE is introduced into the reactor to maintain the pressure of 18-20 kg/cm2 and temperature at 180-190 °C. The temperature of the reactor is maintained to 180-190 °C while maintaining a pressure of 18-20 kg/cm2 for 10 to 12 hours under stirring.

Thereafter, on completion of the reaction; the reaction mixture is cooled down to a temperature of 30 ± 5 °C, recovering the reaction products by filtering the reaction product; optionally washing the reaction product with 5-15% w/w aqueous solution of sodium thiosulphate; collecting the organic layer followed by performing fractional distillation and isolating the individual fractions of various diiodoperfluoroalkanes such 1,2-diiodotetrafluoroethane (C2DI); 1,4-diiodoperfluorobutane (C4DI); 1,6-diiodoperfluorohexane (C6DI); 1,8- diiodoperfluorooctane (C8DI).

The process of the present invention provides diiodoperfluoroalkanes having Gas Chromatography purity of individual fractions not less than 98%. The GC analyses were performed on an Agilent 8890 gas chromatograph, equipped with a flame-ionization detector and an all-glass split-type sample injector. DB 624 (30 m X 0.53 mm X 3 µm) capillary column used in the work. injections were made at 50°C and continue to 240°C with 11.51 ml/min flow rate.

The present invention is more particularly described in the following example that is intended as illustration only, since numerous modifications and variations within the scope of the present invention will be apparent to those skilled in the art. Unless otherwise noted, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples were obtained or are available from the chemical suppliers.

The following examples illustrate the nature of the invention and are provided for illustrative purposes only and should not be construed to limit the scope of the invention.

EXAMPLE 1
710 g (2.797 moles) of iodine introduced into a reaction vessel. After the oxygen (O2) content in the reactor was reduced to less than 20 ppm by applying nitrogen vacuum cycles, the reactor was charged with 15-20 kg/cm2 TFE to initiate the reaction at 180-190°C, once reaction-initiated pressure come down to below 10 kg/cm2, charge multiple time of TFE to maintain the 18-20 kg/cm2 at 180-190°C for 10 -12 hours to consume 677 g (6.770 moles) TFE, After completion of the reaction, the reaction mixture was allowed to cool up to temperature of 30 ± 5°C, unload the reaction mass and washed with 10% sodium thiosulphate (1 volume) at 30 ± 5°C, separated below organic layer. The organic layer product obtained after reaction was analyzed by Gas Chromatography (GC).

The diiodoperfluoroalkanes analyzed for the composition were
1,2-diiodootetrafluoroethane (C2DI) 23%,
1,4-diiodooctafluorobutane(C4DI) 37%;
1,6-diiodoperfluorohexane(C6DI) 23%;
1,8- diiodoperfluorooctane (C8DI) 9%.

This organic layer was subjected for fractional distillation and highly pure fraction were collected based on their boiling points respectively as per table mentioned below for the fractions collection temperature range-

TABLE for diiodoperfluoroalkanes - C2DI, C4DI, C6DI pure fractions recovered after fractional distillation
S. No Product Description Retention time (minute) GC purity (%) Moisture content (w/w %) Boiling point
(°C)
1 C2DI Violet color liquid 8.22 min 99.69 NML 1.0 % 113-114°C
2 C4DI Violet color liquid 12.05 min 99.93 NML 1.0 % 149-150°C
3 C6DI Violet color liquid 15.84 min 98.95 NML 1.0 % 186-188°C
EXAMPLE 2
710 g (2.797 moles) of iodine and 53.2 g (0.280 moles) of copper iodide (Cu I) powder were introduced into a reaction vessel. After the (O2) oxygen content in the reactor was reduced to less than 20 ppm by applying nitrogen vacuum cycles, the reactor was charged with 15-20 kg/cm2 TFE to initiate the reaction at 180-190 °C, once reaction-initiated pressure come down to below 10 kg/cm2, charge multiple time of TFE to maintain the 18-20 kg/cm2 at 180-190°C for 10 -12 hours to consume 677 g (6.770 moles) TFE, After completion of the reaction, the reaction mixture was allowed to 30 ± 5°C, unload the reaction mass, then filtered through a Whatman filter paper to separate the copper iodide powder and washed with 10% sodium thiosulphate (1 volume) at 30 ± 5°C, separated below organic layer. The organic layer product obtained after reaction was analyzed by Gas Chromatography (GC).

The diiodoperfluoroalkanes analyzed for the composition were
1,2-diiodotetrafluoroethane (C2DI) 23%,
1,4-diiodooctafluorobutane (C4DI) 39%;
1,6-diiodoperfluorohexane (C6DI) 22%;
1,8- diiodoperfluorooctane (C8DI) 6%.

This organic layer was subjected for fractional distillation and highly pure fraction were collected respectively.

EXAMPLE 3
468 g (1.842 moles) of iodine and 11.47 g (0.180 moles) of copper powder were introduced into a reaction vessel. After the (O2) oxygen content in the reactor was reduced to less than 20 ppm by applying nitrogen vacuum cycles, the reactor was charged with 15-20 kg/cm2 TFE to initiate the reaction at 180-190 °C, once reaction-initiated pressure come down to below 10 kg/cm2, charge multiple time of TFE to maintain the 18-20 kg/cm2 at 180-190°C for 10 -12 hours to consume 677 g (6.770 moles) TFE, After completion of the reaction, the reaction mixture was allowed to 30 ± 5°C, unload the reaction mass, then filtered through a Whatman filter paper to separate the copper powder and washed with 10% sodium thiosulphate (1 volume) at 30 ± 5°C, separated below organic layer. The organic layer product obtained after reaction was analyzed by Gas Chromatography (GC).

The diiodoperfluoroalkanes analyzed for the composition were
1,2-diiodotetrafluoroethane (C2DI) 11%,
1,4-diiodooctafluorobutane (C4DI) 42%;
1,6-diiodoperfluorohexane (C6DI) 35%;
1,8- diiodoperfluorooctane (C8DI) 6%.

This organic layer was subjected for fractional distillation and highly pure fraction were collected respectively.

EXAMPLE 4
468 g (1.842 moles) of iodine and 11.47 g (0.180 moles) of copper powder were introduced into a reaction vessel. After the (O2) oxygen content in the reactor was reduced to less than 20 ppm by applying nitrogen vacuum cycles, the reactor was charged with 15-20 kg/cm2 TFE to initiate the reaction at 180-190 °C, once reaction-initiated pressure come down to below 10 kg/cm2, charge multiple time of TFE to maintain the 18-20 kg/cm2 at 180-190°C for 10 -12 hours to consume 851 g (8.510 moles) TFE, After completion of the reaction, the reaction mixture was allowed to 30 ± 5°C, unload the reaction mass, then filtered through a Whatman filter paper to separate the copper powder and washed with 10% sodium thiosulphate (1 volume) at 30 ± 5°C, separated below organic layer. The organic layer product obtained after reaction was analyzed by Gas Chromatography (GC).

The diiodoperfluoroalkanes analyzed for the composition were
1,2-diiodotetraluoroethane (C2DI) 15%,
1,4-diiodooctafluorobutane (C4DI) 41%;
1,6-diiodoperfluorohexane (C6DI) 32%;
1,8- diiodoperfluorooctane (C8DI) 7%.

This organic layer was subjected for fractional distillation and highly pure fraction were collected respectively.

EXAMPLE 5
468 g (1.842 moles) of iodine and 11.47 g (0.180 moles) of copper powder were introduced into a reaction vessel. After the (O2) oxygen content in the reactor was reduced to less than 20 ppm by applying nitrogen vacuum cycles, the reactor was charged with 15-20 kg/cm2 TFE to initiate the reaction at 180-190 °C, once reaction-initiated pressure come down to below 10 kg/cm2, charge multiple time of TFE to maintain the 18-20 kg/cm2 at 180-190°C for 10 -12 hours to consume 1054 g (10.540 moles) TFE, After completion of the reaction, the reaction mixture was allowed to 30 ± 5°C, unload the reaction mass, then filtered through a Whatman filter paper to separate the copper powder and washed with 10% sodium thiosulphate (1 volume) at 30 ± 5°C, separated below organic layer. The organic layer product obtained after reaction was analyzed by Gas Chromatography (GC).

The diiodoperfluoroalkanes analyzed for the composition were
1,2-diiodotetrafluoroethane (C2DI) 14%,
1,4-diiodooctafluorobutane (C4DI) 40%;
1,6-diiodoperfluorohexane (C6DI) 32%;
1,8- diiodoperfluorooctane (C8DI) 7%.

This organic layer was subjected for fractional distillation and highly pure fraction were collected respectively.

EXAMPLE 6
50 g (0.196 moles) of iodine and 1.58 g (0.024 moles) of copper powder were introduced into a reaction vessel. After the (O2) oxygen content in the reactor was reduced to less than 20 ppm by applying nitrogen vacuum cycles, the reactor was charged with 15-20 kg/cm2 TFE to initiate the reaction at 180-190 °C, once reaction-initiated pressure come down to below 10 kg/cm2, charge multiple time of TFE to maintain the 18-20 kg/cm2 at 180-190°C for 10 -12 hours to consume 250 g (2.500 moles) TFE, After completion of the reaction, the reaction mixture was allowed to 30 ± 5°C, unload the reaction mass, then filtered through a Whatman filter paper to separate the copper powder and washed with 10% sodium thiosulphate (1 volume) at 30 ± 5°C, separated below organic layer. The organic layer product obtained after reaction was analyzed by Gas Chromatography (GC).
The diiodoperfluoroalkanes analyzed for the composition were
1,2-diiodotetrafluoroethane (C2DI) 12%,
1,4-diiodooctafluorobutane (C4DI) 35%;
1,6-diiodoperfluorohexane (C6DI) 32%;
1,8- diiodoperfluorooctane (C8DI) 7%.

This organic layer was subjected for fractional distillation and highly pure fraction were collected respectively.

The details of varying the molar ratio of iodine and TFE and the optionally added catalyst are provided in the Table below:

S No Iodine(g) TFE(g) TFE Mole ratio per mole of Iodine Catalyst (g) Temp(°C) Product composition %weight I-(C2F4) n-I
n=1 n=2 n=3 n=4
1 710 677 2.42 nil 180-190 23 37 23 9
2 710 677 2.42 53.2 (CuI) 180-190 23 39 22 6
3 468 677 3.675 11.47 (Cu) 180-190 11 42 35 6
4 468 851 4.619 11.47 (Cu) 180-190 15 41 32 7
5 468 1054 5.722 11.47 (Cu) 180-190 14 40 32 7
6 50 250 12.755 1.58 (Cu) 180-190 12 35 32 7
The method of manufacturing diiodoperfluoroalkanes as described in the various embodiments according to the present invention above offers several advantages, including:
a) Single step reaction to produce the various diiodoperfluoroalkanes;
b) High yield of the product;
c) Selectivity of the process that helps minimize unwanted by-products;
d) Environment friendly process;
e) Mild conditions of the process; and
f) Versatility.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore, to be considered in all respects as illustrative and not restrictive.

While certain present preferred embodiments of the invention have been illustrated and described herein, it is to be understood that the invention is not limited thereto. Clearly, the invention may be otherwise variously embodied, and practiced.
,CLAIMS:We claim:

1. A process for synthesizing diiodoperfluoroalkanes comprising the steps of:
a) introducing iodine in the reactor followed by optionally adding catalyst
b) performing the nitrogen purging to reduce the oxygen content to less than 20 ppm
c) add tetrafluoroethylene (TFE) into a reaction vessel;
d) heating the reaction mixture under stirring at temperature ranging between 150- 200°C and time duration ranging between 5-15 hours;
e) cooling the reaction mixture to temperature ranging between 20- 30°C;
f) recovering the diiodoperfluoroalkanes as reaction product

2. The process as claimed in claim 1 for synthesizing diiodoperfluoroalkanes, wherein the step f) of recovering the reaction product comprising the steps of –
a. Optionally filtering the reaction product
b. washing the step a) reaction product
c. collecting the organic layer and performing the fractional distillation
d. isolating the individual fractions of 1,2-diiodotetrafluoroethane (C2DI), 1,4-diiodooctafluorobutane (C4DI); 1,6-diiodoperfluorohexane (C6DI); and 1,8- diiodoperfluorooctane (C8DI)

3. The process as claimed in claim 2 in the step b., wherein the washing is performed using 5-15% w/w aqueous solution of salts.

4. The process as claimed in claim 3, wherein salts for preparing aqueous solution are selected from ammonium thiosulphate, sodium thiosulphate, ascorbic acid, potassium thiosulphate, magnesium chloride, magnesium thiosulphate or mixture thereof.

5. The process as claimed in claim 2 in the step d. having GC purity of individual fractions is not less than 98%.

6. The process as claimed in claim 1 for synthesizing diiodoperfluoroalkanes, wherein the optionally used catalyst is selected from copper or copper iodide or copper chloride or copper bromide.

7. The process as claimed in claim 1, wherein the pressure of the reactor is maintained ranging between 15-25 kg/cm2.

8. The process as claimed in claim 1, wherein the TFE are added in a molar ratio ranging from 2.0 to 15 with respect to 1 mole of iodine.