Production of carboxylic acid halides and carboxylate salts

A process for preparing carboxylic acid halides and carboxylate salts by reacting metal or "onium" halides with carboxylic anhydrides, which process is very suitable for working-up anhydrous, spent catalyst preparations. The resulting carboxylic acid halide or carboxylate salt can be used as an acylating reagent or alkylating reagent, and metal halide or "onium" halide liberated during this can be reacted anew with carboxylic anhydride and regenerated, thereby making it possible to effect a hydrolysis-free alkylation or acylation without forming salt-type waste products. If the mixture of carboxylic acid halide and carboxylate salt is allowed to react with an alcohol, preferably in situ, the resulting ester can be isolated without hydrolysis.

BACKGROUND OF THE INVENTION 
This invention relates to a process for preparing carboxylic acid halides 
and carboxylate salts. 
Carboxylic acid halides, for example trifluoroacetyl chloride, 
trifluoroacetyl bromide or trifluoroacetyl iodide, are valuable 
intermediates in chemical synthesis, for example in the preparation of 
herbicides, surfactants and pharmaceuticals. For example, trifluoroacetyl 
chloride is a polymerization initiator for tetrafluoroethylene. 
Carboxylic acid salts are also valuable intermediates in synthesis. Thus, 
halogen-substituted aromatic compounds can be converted to the 
corresponding trifluoromethylated aromatic compound using sodium 
trifluoroacetate with elimination of sodium chloride and decarboxylation. 
One industrial process for preparing trifluoroacetyl chloride is described 
in U.S. Pat. No. 4,382,897, in which 
1,1,1,-trifluoro-2,2,2,-trichloroethane is reacted with sulfur trioxide in 
the presence of mercury salts and, additionally, boron halide and/or 
halosulfonic acid. The resulting CF.sub.3 C(O) Cl can be converted, for 
example by means of alcohols, to esters of trifluoroacetic acid. 
Carboxylic acid bromides and carboxylic acid iodides can be produced from 
the corresponding carboxylic acid chlorides by using anhydrous hydrogen 
bromide or hydrogen iodide, see R. N. Haszeldine, J. Chem. Soc. 1951, 
pages 584 to 587. Another industrial process for preparing trifluoroacetyl 
bromide and trifluoroacetyl iodide is disclosed in Japanese Patent 
Application No. JP-A 2/262 530. In this process the corresponding acetyl 
fluoride is reacted with lithium bromide or lithium iodide. In addition, 
it is known to prepare trifluoroacetyl halides by reacting trifluoroacetic 
acid anhydride with phosphoric acid chlorides or phosphinic acid 
chlorides. A mixed anhydride of phosphonic acid or phosphinic acid and 
trifluoroacetic acid is formed as a by-product, which is industrially 
worthless. This process is described by J. Helinski et al. in Phosphorus 
Sulfur Silicon Relat. Chem. 54 (1990), pages 225 and 226. Thus, the known 
processes, especially for preparing carboxylic acid halides, are 
technically difficult to carry out, or they form unwanted waste products. 
SUMMARY OF THE INVENTION 
It is the object of the present invention to provide a process particularly 
for preparing carboxylic acid halides. 
Another object of the invention is to provide a process for preparing 
carboxylic acid halides which is technically easy to carry out. 
A further object of the invention is to provide a process for preparing 
carboxylic acid halides which does not produce large amounts of undesired 
waste products. 
Yet another object of the invention is to provide a process for 
simultaneously preparing carboxylic acid halides and carboxylate salts. 
These and other objects of the invention are achieved by providing a 
process for simultaneously preparing a carboxylic acid halide and a 
carboxylate salt formed from carboxylate anions and 1/n cations M.sup.n+ 
selected from the group consisting of metal cations and "onium" cations, 
wherein n+ represents the positive charge of the cation, said process 
comprising reacting a carboxylic anhydride with a compound corresponding 
to the formula M.sup.n+ (Hal.sup.-).sub.n, wherein Hal.sup.- represents 
chloride, bromide or iodide. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
In accordance with the invention carboxylic acid halides and carboxylate 
salts composed of carboxylate anions and 1/n M.sup.n+ cations, where 
M.sup.n+ is the cation of a metal or an "onium" cation and n+ represents 
the positive charge of the cation, are simultaneously produced by reacting 
a carboxylic anhydride with a compound M.sup.n+ (Hal.sup.-).sub.n, where 
Hal.sup.- represents chloride, bromide or iodide. As used herein, the term 
"carboxylic acid halide" refers to a carboxylic acid chloride, bromide or 
iodide. Carboxylic acid chlorides are preferred. 
Advantageously, approximately n equivalents of the carboxylic anhydride, or 
a slight excess, are used. Naturally, it is also possible, with reduced 
yield, to use the carboxylic anhydride in less than equivalent amounts. 
Good results are obtained when 0.95 n to 1.05 n equivalents of the 
carboxylic anhydride are used. For example, it is possible to react 1 mole 
of AlCl.sub.3 (n=3) with 3 moles of acetic acid anhydride to give acetyl 
chloride and aluminum acetate. 
Preferred metal cations are those of groups I, II and III of the periodic 
table, particularly sodium, potassium and aluminum. In the present 
invention "n" is an integer, preferably 1, 2 or 3. 
As used herein, the term "onium" cation refers to a molecule with a 
positively charged nitrogen atom. 
An advantageous property of the process according to the invention is that 
only valuable products are formed without formation of waste products. 
In accordance with a preferred embodiment, the starting material M.sup.n+ 
(Hal.sup.-).sub.n is used in the form of anhydrous waste products, as 
formed in chemical or physical processes. "Onium" halides serve for 
example as catalysts or phase-transfer catalysts, for example in preparing 
organic carbonates from organic acids, carbon monoxide and oxygen and in 
the presence of further catalytically active substances. "Onium" halides 
are also formed, for example, in base-catalyzed reactions of C--H acidic 
compounds, e.g. malonates, with carboxylic acid halides. Metal halides, 
e.g. sodium chloride, contaminated with organic material are a waste 
product in the reaction of sodium salts of carboxylic acids with, for 
example, halogenated aromatics to give alkylated aromatics. Such waste 
products or spent catalysts can be converted to valuable products by the 
process according to the invention. 
According to a variant of the process according to the invention, the 
carboxylic acid halide and the carboxylate salt are not isolated. In this 
variant the reaction mixture containing the carboxylic acid halide and 
carboxylate salt is reacted further to, for example, carboxylic acid 
esters without isolating the carboxylic acid halide and/or the carboxylate 
salt (see below). 
According to another variant of the process according to the invention, the 
reaction mixture is separated into carboxylic acid halide and carboxylate 
salt. This is very readily achieved by evaporating the volatile carboxylic 
acid halide, preferably in vacuo. The separated products can be used as 
intermediates in chemical reactions or as catalysts. 
From the foregoing it can be seen that the reaction products obtained from 
the reaction of metal halides or "onium" halides with carboxylic 
anhydrides can be used in processes in which metal halides or "onium" 
halides are liberated again, for example in acylation processes, 
alkylation processes, esterification or in preparing ketones. The 
liberated halide can be reacted anew with carboxylic anhydride and 
regenerated again. In this manner it is possible to carry out an 
acylation, alkylation, esterification or preparation of ketones without 
forming waste salts and or needing a hydrolysis step. This embodiment of 
the process according to the invention is particularly preferred and 
characterized by the use of the carboxylic acid halide and/or carboxylate 
salt in reactions where M.sup.n+ (Hal.sup.-).sub.n is liberated anew and 
reacted again with carboxylic anhydride and regenerated. In this manner a 
continuous or semi-continuous procedure is possible without salts being 
formed. In addition, a hydrolysis-free procedure is possible. 
In principle the process according to the invention is suitable for 
reacting any halides with any carboxylic anhydrides. In some cases, 
however, in order to increase the rate of the reaction it is desirable to 
use an aprotic solvent for the anhydride, for example a hydrocarbon or a 
monomeric, oligomeric or polymeric ether, or an aprotic solvent for the 
halide, for example one of the known polar solvents such as nitriles, 
lactams, ethers, etc. If desired, the rate of reaction can also be 
increased by the addition of phase-transfer catalysts such as crown 
ethers. 
Very good results are obtained when carboxylic anhydrides of carboxylic 
acids with 2 to 4 carbon atoms are used. It is particularly advantageous 
to use carboxylic anhydrides of carboxylic acids with 2 to 4 carbon atoms 
which are substituted with 1 to 7 halogen atoms, preferably 1 to 7 
fluorine atoms, such as, for example, trifluoroacetic anhydride. 
Sodium halide or potassium halide or an "onium" halide of nitrogen is 
preferably used as the halide. Halide preferably represents chlorine, 
bromine and iodine, particularly chlorine and bromine. Especially good 
results with surprisingly high yields are obtained when "onium" halide is 
used in the process according to the invention. Thus, M.sup.n+ preferably 
represents an "onium" cation of nitrogen corresponding to the formula 
R.sup.1 R.sup.2 R.sup.3 R.sup.4 N.sup.+, in which R.sup.1, R.sup.2, 
R.sup.3 and R.sup.4 are independently selected from hydrogen, alkyl with 1 
to 20 carbon atoms, aryl or aralkyl, or in which R.sup.1 and R.sup.2, or 
in which R.sup.3 and R.sup.4, or in which R.sup.1, R.sup.2 and R.sup.3, or 
in which R.sup.1, R.sup.2, R.sup.3 and R.sup.4, where appropriate with 
inclusion of the nitrogen atom, form saturated or unsaturated ring 
systems, in particular heteroaromatic compounds. Aryl here represents 
particularly phenyl and phenyl substituted by 1 or more halogen atoms 
and/or substituted by 1 or more C1-C2-alkyl groups. Salts in which 
M.sup.n+ represents ammonium, piperidinium, pyridinium or R.sup.1' 
R.sup.2' R.sup.3' R.sup.4' N.sup.+, in which R.sup.1', R.sup.2', R.sup.3' 
and R.sup.4' are, independently of each other, hydrogen, alkyl with 1 to 
15 carbon atoms or benzyl are particularly suitable. Good examples which 
may be mentioned include pyridinium hydrohalides, anilinium hydrohalides, 
piperidinium hydrohalides, benzyltriethylammonium hydrohalides and 
triethylammonium hydrohalides, preferably the chlorides and bromides, 
particularly the chlorides. 
In a particularly preferred variant of the invention, the mixture of 
carboxylic acid halide and carboxylate salt is reacted with an alcohol 
with the formation of a carboxylic acid ester, during or after the 
preparation of the mixture. Many esters of carboxylic acids are used as 
such industrially. Acetic acid esters and other carboxylic acid esters 
serve, for example, as solvents or detergents. Other esters, e.g. of 
succinic acid, are used in aromatization. Ethyl trifluoroacetate, for 
example, is a solvent for the chlorination of paraffins or the 
polymerization of olefin oxides. Many carboxylic acid esters are also 
intermediates in chemical synthesis. Methyl trifluoroacetate and 
1,1,1-trifluoroethyl trifluoroacetate yield trifluoroethanol after 
hydrogenation. Trifluoroethanol is used as a solvent and as an 
intermediate, for example in the preparation of the solvent and 
anaesthetic isoflurane. Esters of trifluoroacetic acid also serve for the 
introduction and preparation of biologically active compounds which 
contain CF.sub.3 groups. For example, N-acylation with methyl 
trifluoroacetate can be used to produce peptides with hormonal activity. 
Ethyl trifluoroacetate reacts with camphor derivatives to yield shift 
reagents for NMR analysis. The trifluoromethylphenyl ester yields, after a 
Fries migration with aluminum chloride, the corresponding 
trifluoroacetylated phenol, which is a synthetic building block for 
pharmaceuticals. Many other uses of esters are known to those skilled in 
the art, for example use in preparing pharmaceuticals, photosensitizers 
and dyes. 
The preparation of carboxylic acid esters is normally carried out by 
reacting the corresponding alcohols with the carboxylic acids under acid 
catalysis. The resulting water of reaction has to be removed to shift the 
equilibrium of the reaction. In the case of fluorinated derivatives this 
can lead to difficulties because of the preferred binding of water (to the 
carbonyl functions as hydrates). It is also already known that carboxylic 
acid esters can be produced from carboxylic acid chlorides and alcohols 
with base catalysis. However, hydrolytic work-up is necessary, and in 
addition waste salts are formed, for example pyridine hydrochloride, which 
have to be disposed of. The reaction of carboxylic acid halides with 
alcohols proceeds at a reduced rate of reaction without base catalysis. 
The invention is based on the knowledge that the resulting product mixture, 
which contains carboxylic acid halide and carboxylate salt, yields 
carboxylic acid esters with alcohols. The carboxylate salt surprisingly 
shows catalytic activity. 
Naturally, it is possible first to isolate the carboxylic acid halide and 
carboxylate salt separately and then react them in the desired amounts 
with alcohol. 
It is also possible, but not required, to add acid, e.g. a carboxylic acid. 
Preferably acid is not added, particularly in the case of in situ 
esterification. 
The preferred starting materials for preparing esters are carboxylic acid 
chlorides. Preferably, an "onium" salt of the carboxylic acid is used as 
catalyst. 
The variant of the process according to the invention can in principle be 
used for preparing any esters of any carboxylic acids with any alcohols. A 
preferred embodiment of the variant comprises using a carboxylic acid 
chloride of the formula R.sup.a C(O)Cl (I), in which R.sup.a is alkyl with 
1 to 6 carbon atoms; alkyl with 1 to 6 carbon atoms substituted by at 
least 1 halogen atom; phenyl; tolyl; phenyl or tolyl substituted by at 
least 1 halogen atom. 
In addition, it is preferred to use an alcohol of the formula R.sup.b OH 
(II) in which R.sup.b is alkyl or alkenyl with 1 to 8 carbon atoms, alkyl 
or alkenyl with 1 to 8 carbon atoms substituted by at least 1 halogen 
atom; phenyl; tolyl; benzyl; phenyl, tolyl or benzyl substituted by at 
least 1 halogen atom and/or at least a nitro group. 
It is very particularly preferred when R.sup.a is alkyl with 1 to 4 carbon 
atoms substituted with at least 1 fluorine atom and R.sup.b is alkyl or 
alkenyl with 1 to 4 carbon atoms; alkyl or alkenyl with 1 to 4 carbon 
atoms substituted by at least 1 halogen atom; phenyl; phenyl substituted 
by at least 1 halogen atom and/or at least one nitro group, especially 
perfluoromethyl, perfluoroethyl or perfluoropropyl. Particularly 
preferably, R.sup.b is alkyl or alkenyl with 1 to 3 carbon atoms; alkyl or 
alkenyl with 1 to 3 carbon atoms substituted by at least 1 fluorine atom; 
phenyl; phenyl substituted by at least 1 fluorine atom and/or at least one 
nitro group. Alkenyl, of course, denotes an organic group with at least 
two carbon atoms. 
The process variant is particularly well suited for preparing esters of 
acetic acid which is substituted by one or more fluorine atoms. For 
example, phenyl trifluoroacetate can be prepared by the process according 
to the invention. The process according to the invention is particularly 
well suited for preparing esters of trifluoroacetic acid or 
chlorodifluoroacetic acid with 1,1,1-trifluoroethanol, 
pentafluoropropanol, methanol, ethanol, isopropanol, 4-nitrophenol, 
pentafluorophenol and allyl alcohol. 
The molar ratio between carboxylic acid halide and alcohol is 
advantageously above 0.9. The alcohol can also be used in large excess and 
serve as a solvent, particularly when it is an alcohol substituted by 
electron-withdrawing groups such as fluorine atoms. Advantageously, the 
molar ratio between the alcohol and the carboxylic acid halide lies 
between 0.9:1 and 5:1. 
The temperature at which the reaction is carried out lies between ambient 
temperature (about 20.degree. C.) up to the boiling point of the mixture, 
for example up to 100.degree. C. The process is carried out under ambient 
pressure (about 1 bar absolute) or optionally at elevated pressure, for 
example up to 5 bar absolute. 
The alkali metal salt or "onium" salt can be present in catalytic or molar 
amounts. Advantageously, the molar ratio between acid halide and the 
carboxylic acid salt lies in the range from 1:1 to 20,000:1. 
In accordance with a particularly preferred embodiment of the invention, 
the acid chloride or the acid bromide and the alkali metal or "onium salt" 
of the carboxylic acid are produced in situ. For this purpose, the 
corresponding alkali metal halide or "onium" halide, preferably the 
chloride or bromide, particularly the chloride, is reacted with the 
anhydride of the carboxylic acid to be used. In this reaction the 
corresponding acid halide and the corresponding salt form from the 
anhydride of the carboxylic acid. Spent halide catalysts can be used in 
this embodiment as the alkali metal halide or "onium" halide, and can be 
converted in this manner into valuable products. 
The process according to the invention has many advantages. For example it 
works at ambient temperature, although, if desired, the temperature can be 
raised to, for example, 60.degree. C. or higher. In addition the process 
according to the invention can be used to produce special acid halides 
which are difficult to obtain by other processes. In addition, salts which 
are produced as waste in industrial processes can be converted into 
valuable products. It is particularly advantageous to use of the process 
according to the invention when salts are converted to carboxylic acid 
halides and carboxylic acid salts, which when further processed produce 
salts again, which can be regenerated anew in the process according to the 
invention. This procedure makes it possible for the first time to carry 
out a multiplicity of reactions in such a way that no salt waste is 
produced and/or no hydrolytic work-up is necessary. 
The variant of the invention with esterification has the advantage that 
carboxylic acid esters can be produced in a technically simple way without 
hydrolytic work-up. In addition, with most esters, no waste products such 
as pyridine hydrochloride are produced.

The following examples are intended to illustrate the invention in further 
detail without limiting its scope. 
EXAMPLE 1 
Preparation of trifluoroacetyl chloride and pyridinium trifluoroacetate by 
reaction of pyridinium hydrochloride with trifluoroacetic anhydride. 
EQU Py-HCl+[CF.sub.3 C(O)].sub.2 O.fwdarw.CF.sub.3 C(O)Cl+CF.sub.3 C(O)O.PyH 
With exclusion of moisture (N.sub.2 atmosphere), 26.17 g (0.226 mole) of 
pyridinium hydrochloride were taken up in 25 ml of trifluoroacetic acid, 
and 61.84 (0.227 mole) of trifluoroacetic acid anhydride were continuously 
added dropwise with stirring over one hour at room temperature. 
Immediately after the addition of a few drops of trifluoroacetic 
anhydride, vigorous evolution of gas was observed in the reaction flask. 
The resulting trifluoroacetyl chloride was condensed in cold traps cooled 
to -78.degree. C. After completion of trifluoroacetic anhydride addition, 
the reaction solution was warmed to 40.degree. C. for one hour to expel 
dissolved trifluoroacetyl chloride. The yield of trifluoroacetyl chloride 
condensed in was 27.95 g (92.5% of theoretical). A chloride determination 
gave a residual chlorine content of 626.2 mg of chloride (17.66 mmole) in 
the reaction solution. This corresponds to a conversion yield of greater 
than 99%. 
The reaction residue contained pyridinium trifluoroacetate as well as some 
trifluoroacetic acid, which was removed by spray drying. To prepare larger 
amounts the example was repeated several times. 
EXAMPLE 2 
Preparation of trifluoroacetyl chloride and piperidinium trifluoroacetate 
by reaction of piperidinium hydrochloride with trifluoroacetic anhydride. 
EQU Pip.HCl+[CF.sub.3 C(O)].sub.2 O.fwdarw.CF.sub.3 C(O)Cl+CF.sub.3 C(O)O.PipH 
With exclusion of moisture (N.sub.2 atmosphere), 27.26 g (0.226 mole) of 
piperidinium hydrochloride were taken up in 25 ml of trifluoroacetic acid 
and 61.84 g (0.227 mole) of trifluoroacetic anhydride were added 
continuously dropwise with stirring within one hour at room temperature. 
Immediately after the addition of a few drops of trifluoroacetic 
anhydride, vigorous evolution of gas was observed in the reaction flask. 
The resulting trifluoroacetyl chloride was condensed in cold traps cooled 
to -78.degree. C. After completion of trifluoroacetic anhydride addition, 
the reaction solution was warmed to 40.degree. C. for one hour to expel 
dissolved trifluoroacetyl chloride. The yield of trifluoroacetyl chloride 
condensed in was 26.97 g (89.9 % of theoretical). A chloride determination 
gave a residual chlorine content of 778.8 mg of chloride (21.97 mmole) in 
the reaction solution. This corresponds to a conversion yield of 99.8%. 
EXAMPLE 3 
Preparation of trifluoroacetyl chloride and benzyltriethylammonium 
trifluoroacetate by reaction of benzyltriethylammonium hydrochloride with 
trifluoroacetic anhydride. 
EQU (C.sub.6 H.sub.5 CH.sub.2)Et.sub.3 N.Cl+[CF.sub.3 C(O)].sub.2 
O.fwdarw.CF.sub.3 C(O)Cl+CF.sub.3 C(O)O.NEt.sub.3 (C.sub.6 H.sub.5 
CH.sub.2) 
With exclusion of moisture (N.sub.2 atmosphere), 43.55 g (0.191 mole) of 
benzyltriethylammonium hydrochloride were taken up with 21 ml of 
trifluoroacetic acid and 52.20 g (0.249 mole) of trifluoroacetic anhydride 
were added continuously dropwise with stirring within one hour at room 
temperature. Immediately after the addition of a few drops of 
trifluoroacetic anhydride, vigorous evolution of gas was observed in the 
reaction flask. The resulting trifluoroacetyl chloride was condensed in 
cold traps cooled to -78.degree. C. After completion of trifluoroacetic 
anhydride addition, the reaction solution was warmed to 40.degree. C. for 
one hour to expel dissolved trifluoroacetyl chloride. 
The yield of condensed trifluoroacetyl chloride was 20.26 g (80.1% of 
theoretical). A chloride determination gave a residual chlorine content of 
15.3 mg (0.432 mmole) of chloride in the reaction solution. This 
corresponds to a conversion yield of 87.1%. 
EXAMPLE 4 
Preparation of trifluoroacetyl chloride and triethylammonium 
trifluoroacetate by reaction of triethylammonium hydrochloride with 
trifluoroacetic anhydride. 
EQU Et.sub.3 N.HCl+[CF.sub.3 C(O)].sub.2 O.fwdarw.CF.sub.3 C(O)Cl+CF.sub.3 
C(O)O.NHEt.sub.3 
With exclusion of moisture (N.sub.2 atmosphere), 31,11 g (0.226 mole) of 
triethylammonium hydrochloride were taken up in 25 ml of trifluoroacetic 
acid and 61.84 g (0.294 mole) of trifluoroacetic anhydride were added 
continuously dropwise with stirring within one hour at room temperature. 
Immediately after addition of a few drops of trifluoroacetic anhydride, 
vigorous evolution of gas was observed in the reaction flask. The 
resulting trifluoroacetyl chloride was condensed in cold traps cooled to 
-78.degree. C. After completion of trifluoroacetic anhydride addition, the 
reaction solution was warmed to 40.degree. C. for one hour to expel 
dissolved trifluoroacetyl chloride. The yield of trifluoroacetyl chloride 
condensed in was 19.82 g (66.1% of theoretical). A chloride determination 
gave a residual chlorine content of 1.16 g of chloride (32.7 mmole) in the 
reaction solution. This corresponds to a conversion yield of 77.4%. 
EXAMPLE 5 
Preparation of trifluoroacetyl bromide and pyridinium trifluoroacetate by 
reaction of pyridinium hydrobromide with trifluoroacetic anhydride. 
EQU Py.HBr+[CF.sub.3 C(O)].sub.2 O.fwdarw.CF.sub.3 C(O)Br+CF.sub.3 C(O)O.PyH 
With exclusion of moisture (N.sub.2 atmosphere), 36.16 g (0.226 mole) of 
pyridinium hydrobromide were taken up in 25 ml of trifluoroacetic acid and 
61.84 g (0.294 mole) of trifluoroacetic anhydride were added continuously 
dropwise with stirring within one hour at room temperature. Immediately 
after addition of a few drops of trifluoroacetic anhydride, vigorous 
evolution of gas was observed in the reaction flask. The resulting 
trifluoroacetyl bromide was condensed in cold traps cooled to -78.degree. 
C. After completion of trifluoroacetic anhydride addition, the reaction 
solution was warmed to 40.degree. C. for one hour to expel dissolved 
trifluoroacetyl bromide. The yield of trifluoroacetyl bromide condensed in 
was 28.18 g (70.5 of theoretical). A bromide determination gave a residual 
bromine content of 4.90 g of bromide (61.3 mmole) in the reaction 
solution. This corresponds to a conversion yield of 96.7%. 
EXAMPLE 6 
Preparation of trifluoroacetyl chloride and sodium trifluoroacetate by 
reaction of sodium chloride with trifluoroacetic anhydride in the presence 
of crown ethers. 
EQU NaCl+[CF.sub.3 C(O)].sub.2 O.fwdarw.CF.sub.3 C(O)Cl+CF.sub.3 C(O)O.Na 
With exclusion of moisture, 13.25 g (0.226 mole) of NaCl and 1.03 g (0.004 
mole) of 18-crown-6 were taken up in 25 ml of trifluoroacetic acid and 32 
ml (0.227 mole) of trifluoroacetic anhydride were added dropwise with 
stirring at room temperature. The resulting trifluoroacetyl chloride was 
condensed in cold traps cooled to -78.degree. C. After completion of 
trifluoroacetic anhydride addition, stirring was continued at room 
temperature for about 42 hours. The yield of trifluoroacetyl chloride 
condensed in the cold traps was 28.29 g (55.90% of theoretical). A 
chloride determination gave a residual chlorine content of 2.95 g of 
chloride (83.2 mmole) in the reaction solution. This corresponds to a 
conversion yield of 63.3%. 
EXAMPLE 7 
Preparation of trifluoroacetyl iodide and sodium trifluoroacetate by 
reaction of sodium iodide with trifluoroacetic anhydride. 
EQU NaI+[CF.sub.3 C(O)].sub.2 O.fwdarw.CF.sub.3 C(O)I+CF.sub.3 C(O)O.Na 
With exclusion of moisture, 34 g (0.227 mole) of sodium iodide and 1.03 g 
(0.004 mole) of 18-crown-6 were taken up in 25 ml of trifluoroacetic acid 
and 32 ml (0.227 mole) of trifluoroacetic anhydride were added dropwise 
with stirring at room temperature. The solution in the reaction flask 
solidified immediately after the addition of trifluoroacetic anhydride. 
Therefore, a further 25 ml of trifluoroacetic acid were added. The 
resulting acetyl iodide was condensed in cold traps cooled to -78.degree. 
C. After completion of trifluoroacetic anhydride addition, stirring was 
continued for about 16 hours at room temperature. The next day, the 
reaction flask was placed in a water bath containing water at 50.degree. 
C. for about 8 hours, during which time the temperature in the reaction 
flask rose to 40.degree. C. The yield of trifluoroacetyl iodide was 17.23 
g (33,90 of theoretical). An iodide determination gave a residual iodide 
content of 11.17 g of iodide (75.5 mmole) in the reaction solution. This 
corresponds to a conversion yield of 50.5%. 
EXAMPLE 8 
Preparation of trifluoroacetyl iodide and potassium trifluoroacetate by 
reaction of potassium iodide with trifluoroacetic anhydride. 
EQU KI+[CF.sub.3 C(O)].sub.2 O.fwdarw.CF.sub.3 C(O)I+CF.sub.3 C(O)O.K 
With exclusion of moisture, 37.48 g (0.226 mole) of potassium iodide and 
0.99 g (0.004 mole) of crown ether were taken up in 25 ml of 
trifluoroacetic acid, and 32 ml (0.227 mole) of trifluoroacetic anhydride 
were added dropwise with stirring at room temperature. The resulting 
trifluoroacetyl iodide was condensed in cold traps cooled to -78.degree. 
C. After completion of trifluoroacetic anhydride addition, stirring was 
continued for about 12 hours at room temperature. The next day, the 
reaction flask was placed in a water bath containing water at 40.degree. 
C. for about 10 hours. The yield of trifluoroacetyl iodide was 20.06 g 
(39.64 of theoretical). An iodide determination gave a residual iodide 
content of 2.60 g of iodide (21.0 mmole) in the reaction solution. This 
corresponds to a conversion yield of 43.9%. 
EXAMPLE 9 
Preparation of acetyl chloride and pyridinium acetate by reaction of acetic 
anhydride with pyridinium chloride. 
EQU Py.HCl+[CF.sub.3 C(O)].sub.2 O.fwdarw.CH.sub.3 C(O)Cl+CH.sub.3 C(O)O.PyH 
With exclusion of moisture, 45.33 g (0.392 mole) of pyridinium 
hydrochloride were taken up in 30 ml of acetic acid in a Claisen apparatus 
and combined with 36 ml (0.381 mole) of acetic anhydride with stirring at 
room temperature. Subsequently the temperature was raised to 100.degree. 
C. in an oil bath, and the temperature was raised slowly to 170.degree. C. 
over the course of 7 hours. The resulting acetyl chloride was collected in 
a receiver cooled to 10.degree. C., along with anhydride and acetic acid 
which also distilled over. The isolated yield of acetyl chloride in the 
receiver after this reaction period was 7.1% of theoretical. The 
conversion was about 10%. 
In Examples 6 to 8, 18-crown-6 was used. The reactions described in the 
examples also proceed without addition of crown ethers, but the rate of 
reaction is reduced. 
EXAMPLE 10 
Preparation of trifluoroacetyl chloride and aluminum trifluoroacetate by 
reaction of aluminum trichloride with trifluoroacetic anhydride. 
EQU AlCl.sub.3 +3(CF.sub.3 CO).sub.2 O.fwdarw.3CF.sub.3 
COCl+Al(OCOCF.sub.3).sub.3 
With exclusion of moisture (N.sub.2 atmosphere), 39.2 g (0.294 mole) of 
AlCl.sub.3 were taken up in 147 ml of 1,4-dioxane and on three consecutive 
days a total of 185.25 g (0.882 mole) of trifluoroacetic anhydride (one 
equivalent (CF.sub.3 CO).sub.2 O relative to AlCl.sub.3 per day), were 
added continuously dropwise with stirring within one hour at room 
temperature. Immediately after addition of a few drops of trifluoroacetic 
anhydride, evolution of gas was observed in the reaction flask. The 
resulting trifluoroacetyl chloride was condensed in cold traps cooled to 
-78.degree. C. After completion of the trifluoroacetic anhydride addition, 
the reaction solution was heated to 40.degree. C. for two hours to expel 
dissolved trifluoroacetyl chloride. The total isolated yield of condensed 
trifluoroacetyl chloride over all three days was 111.72 g, which 
corresponds to 95.9% of theoretical. 
EXAMPLE 11 
Preparation of trifluoroethyl trifluoroacetate by reacting trifluoroacetyl 
chloride with 2,2,2-trifluoroethanol in the presence of pyridinium 
trifluoroacetate. 
##STR1## 
30 g (0.16 mole) of the pyridinium trifluoroacetate obtained from Example 1 
were taken up in 335 g (3.55 mole) of 2,2,2-trifluoroethanol and 
circulated in a laboratory scale circulation apparatus (1 liter 
four-necked flask fitted with precision glass stirrer, prominent pump, 30 
cm column packed with Raschig rings) at an internal temperature of 
54.degree. C. Subsequently, 134 g (1.01 mole) of trifluoroacetyl chloride, 
obtained in an analogous manner to Example 1, were metered into the flask 
via an immersion tube over 100 min. After completion of the 
trifluoroacetyl chloride addition, the reaction was allowed to continue 
for 10 minutes. Subsequently the reaction mixture was subjected to 
fractional distillation via a Vigreux column (distillation temperature 
54.degree. C. to 56.degree. C.) to give 177.8 g of trifluoroacetyl 
trifluoroacetate, corresponding to a yield of 89.8% of the theoretical. 
The trifluoroethanol/pyridinium salt mixture remaining in the receiving 
flask can be used again for esterification with the same effectiveness. 
EXAMPLES 12-17 
Preparation of trifluoroacetic acid esters by reaction of trifluoroacetyl 
chloride with methanol, ethanol, isopropanol, 4-nitrophenol, 
pentafluorophenol and allyl alcohol in the presence of pyridinium 
trifluoroacetate. 
In an analogous manner to Example 11, the corresponding esters of 
trifluoroacetyl chloride with methanol (94%), ethanol (96%), isopropanol 
(89%), 4-nitrophenol (85%), pentafluorophenol (92%) and allyl alcohol 
(81%) were also prepared. 
EXAMPLE 18 
Preparation of 1,1,1-trifluoroethyl trifluoroacetate in the presence of 
piperidinium trifluoroacetate. 
In an analogous manner to Example 2, starting from trifluoroacetic 
anhydride and piperidinium chloride, trifluoroacetyl chloride and 
piperidinium trifluoroacetate were prepared and isolated. Then 
1,1,1-trifluoroethyl trifluoroacetate was prepared in an analogous manner 
to Example 11. 
EXAMPLE 19 
Preparation of trifluoroethyl trifluoroacetate by reaction of 
trifluoroacetic anhydride with 2,2,2-trifluoroethanol in the presence of 
pyridinium hydrochloride ("in situ" method). 
EQU Py.HCl+(CF.sub.3 CO).sub.2 O+CF.sub.3 CO.sub.2.sup.-.PyH+CF.sub.3 
COCl.sup.CF.sbsp.3.sup.CH.sbsp.2.sup.OH &gt;CF.sub.3 CO-OCH.sub.2 CF.sub.3 
+PyTFA+HCl 
23.11 g (0.2 mole) of pyridinium hydrochloride and 20.0 g (0.2 mole) of 
2,2,2-trifluoroethanol were placed in a 250 ml three-necked flask with a 
precision glass stirrer, dry ice condenser and dropping funnel. 
Subsequently, 42.01 g (0.2 mole) of trifluoroacetic anhydride were added 
dropwise over 3 hours at an internal reaction temperature of 52.degree. C. 
to 55.degree. C. The yield of trifluoroethyl trifluoroacetate was 98% 
(GC). 
The foregoing description and examples have been set forth merely to 
illustrate the invention and are not intended to be limiting. Since 
modifications of the disclosed embodiments incorporating the spirit and 
substance of the invention may occur to persons skilled in the art, the 
invention should be construed to include everything within the scope of 
the appended claims and equivalents thereof.