Method of producing acid fluorides from acid chlorides

Details Method of producing acid fluorides from acid chlorides Method of producing acid fluorides from acid chlorides

2001-05-30

2004-04-20

Rotman, Alan L. (Department: 1625)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic halides

C423S468000

Reexamination Certificate

active

06723874

ABSTRACT:

The invention relates to a method of producing acid fluorides from acid chlorides by contacting with hydrogen fluoride adducts of nitrogen-base hydrofluorides.
Acid fluorides, for example carboxylic acid fluorides and sulphuryl fluoride, are advantageous products for use per se or as intermediate products. Sulphuryl fluoride, for example, can be used as a fumigant for vermin, e.g. in wood used in buildings, churches, museums, silos and buildings, and to counteract discolouring enzymes, fungi or pathogens in wood which has not been used for building, e.g. freshly felled wood. Carboxylic acid fluorides are valuable intermediate products in chemical synthesis. Sulphuryl chloride fluoride can be reacted to form sulphuryl fluoride.
German Offenlegungsschrift DE-OS 28 23 969 discloses the preparation of fluorocarbonyl compounds from chlorocarbonyl compounds, for example of chlorodifluoroacetyl fluoride from chlorodifluoroacetyl chloride and HF adducts of hydrofluorides of organic nitrogen bases as fluorination agents. If HF adducts are used, amine is added to bind HF, or solvents having sufficient alkalinity are used to bind HF.
It was an object of the present invention to devise an improved fluorination process for the preparation of acid fluorides from acid chlorides. This object is achieved by the method of the present invention.
The method according to the invention provides for acid fluorides to be prepared from acid chlorides by contacting with hydrogen fluoride adducts of hydrofluorides of organic nitrogen bases or ammonium fluoride. In this case, the method is carried out so that, unlike in the prior art, no base which has an HF-binding effect is added. Nor is any solvent which binds HF used. At best, if in accordance with an embodiment to be described hereafter an acid is added, such as trifluoroacetic acid, this acid or part of this acid may be neutralised by base, by adding a desired quantity of base before, during or after the addition of acid. However, HF is not bound.
In addition to HF adducts of ammonium fluoride, the HF adducts of hydrofluorides of organic nitrogen bases named in German Offenlegungsschrift DE-OS 28 23 969 can be used for contacting. They can be expressed by the formula B.(HF)
x
, wherein B represents an organic nitrogen base and x is a whole number or a fraction from <1 to 4, preferably 2-3.
Any possible primary, secondary and/or tertiary amines including N-heterocycles may be used as organic nitrogen bases B. If these amines are represented by the formula:
R
1
R
2
R
3
N
the meanings therein could be as follows:
R
1
an alkyl radical, preferably having 1 to 10, in
particular 1 to 6, C atoms,
a cycloalkyl radical, preferably having 5 to 7 C
atoms,
an aralkyl radical, preferably having 6 to
10 C atoms,
or
an aryl radical, preferably likewise having 6 to
10 C atoms;
R
2
and R
3
hydrogen,
alkyl, cycloalkyl, aralkyl and aryl radicals of
the same type as stated under R
1
.
The radicals R
2
and R
3
may be identical or different. Two of the radicals R
1
and R
2
or R
3
may also be closed to form a cycloaliphatic ring, which may optionally be interrupted by other heteroatoms such as oxygen atoms. Likewise, it is possible for the three radicals R
1
, R
2
and R
3
to be constituents of a heterocyclic ring, which means that corresponding N-heterocycles then result. Preferred organic nitrogen bases B are primary, secondary and/or tertiary amines having a total of up to 12 C atoms, the secondary and/or tertiary aliphatic amines being particularly preferred.
Concrete examples of the bases B are:
N-butylamine, N-decylamine, diethylamine, di-n-octylamine, trimethylamine, triethylamine, tri-n-propylamine, isopropyl diethylamine, tri-n-butylamine, cyclohexylamine, N-methylaniline, N,N-dimethylaniline, pyrrolidine, piperidine, N-methylpiperidine, morpholine, pyridine, quinoline, etc.
The HF adducts of the hydrofluorides of the nitrogen bases B can easily be obtained from the bases B and hydrogen fluoride; they are low-melting substances, or substances which are liquid at room temperature, with considerable thermal loading ability. The tris-hydrofluorides can even be vacuum-distilled in non-decomposed form.
Preferably HF adducts of primary, secondary or tertiary amine hydrofluorides having up to 15 C atoms are used, in particular secondary and tertiary amine hydrofluorides. HF adducts of tri-n-propylamine hydrofluoride, tri-iso-propylamine hydrofluoride, tri-n-butylamine hydrofluoride, pyridine hydrofluoride, piperidine hydrofluoride or N,N-dimethylamine hydrofluoride are particularly well suited.
The reaction is performed in liquid phase.
The method according to the invention may be performed batchwise or continuously. In the continuous procedure, the procedure may consist of also feeding in HF, fresh HF adduct or both in addition to the acid chloride to be fluorinated. Correspondingly, reaction mixture is separated off or gaseous reaction products are distilled off or removed in gaseous form.
The inventors have discovered that HCl becomes enriched in the reaction mixture over time. If HF is not fed in intermittently or continuously, the reaction mixture or the HF adduct becomes depleted in HF. It has been discovered that the HF adduct can be regenerated by treating with HF, optionally at elevated temperature (80 to 120° C.) and elevated pressure (e.g. autogenous pressure in an autoclave). In so doing, it was shown that it is not necessary completely to expel any HCl present. A residual content of e.g. less than 5% by weight, preferably less than 2% by weight, HCl is acceptable.
According to one embodiment of the invention, sulphuryl fluoride as acid fluoride is prepared from sulphuryl chloride or sulphur dioxide and chlorine (then under pressure for liquefaction). Here, in order to release HCl, an acid is added, for example a halogenated carboxylic acid such as trifluoroacetic acid. A nitrogen base may be added for (partial) neutralisation of this added acid. In that case, this base expediently corresponds to the base contained in the hydrofluoride.
Sulphuryl fluoride may also be prepared from sulphuryl chloride fluoride. Thus two-stage preparation of sulphuryl fluoride is possible. The first stage comprises the preparation of sulphuryl chloride fluoride from sulphuryl chloride. The ratio of amine (or NH
3
) to HF in the reaction mixture is not limited in this stage; it can also be performed with a very high HF content, e.g. at a ratio of amine to HF of 1:3 up to 1:10 or even above. The second stage, the fluorination of sulphuryl chloride fluoride to sulphuryl fluoride, requires a ratio of amine to HF which is greater than 1:3; for example, it is between 1:2 and 1:3. This proviso in terms of the maximum content of HF in the reaction mixture also applies to one-stage preparation of SO
2
F
2
from SO
2
Cl
2
, if a good yield of SO
2
F
2
is to be obtained. It is assumed that for a ratio of amine to HF of less than 1:3 the reactivity (nucleophilic character) of the F
−
anion changes.
The two-stage preparation of sulphuryl fluoride makes it possible to use a particular method variant, because it has been established that it is simultaneously possible to regenerate the HF adduct (as mentioned above) during the fluorination of SO
2
Cl
2
to SO
2
ClF. SO
2
Cl
2
, an excess of HF and HF adduct which is to be regenerated are introduced into a reactor. At elevated pressure (e.g. autogenous pressure in an autoclave), SO
2
ClF and regenerated HF adduct are produced simultaneously. Gaseous HCl which forms is separated off (e.g. by letting off the superatmospheric pressure and passing though inert gas such as N
2
). Then HF is evaporated off, in order to bring the HF content to within the limits described above (amine : HF>1:3). Then the second stage can be performed for the preparation of SO
2
F
2
. If the first and second stages are performed in the same reactor, it is thus possible always to enter the second stage with re-fluorinated HF adduct.
According to another embodiment, carboxylic acid fluorides of Formula I
 RC(O)F
are prepared in which R stands for

Affiliated with

Also associated with

Rating

Method of producing acid fluorides from acid chlorides does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of producing acid fluorides from acid chlorides, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing acid fluorides from acid chlorides will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3211442