Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
2002-08-30
2004-09-21
Price, Elvis O. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
C570S216000
Reexamination Certificate
active
06794551
ABSTRACT:
BACKGROUND
Propargyl bromide (3-bromopropyne) is known to be useful as a soil fumigant for control of fungi, nematodes, and undesirable plant life. See for example U.S. Pat. No. 2,794,727. It is believed that propargyl bromide is a good replacement for methyl bromide. See K. C. Barrons,
Farm Chemicals International
, 2000 35-36.
A typical process for producing propargyl bromide involves low temperature initiation of reaction of propargyl alcohol and phosphorus tribromide in a liquid phase in the presence of base which usually is a tertiary amine such as triethylamine. While workable, undesirable amounts of waxy solids are often formed in the reaction mixture. Further, because the reaction is exothermic, the requirement for low temperatures (e.g., 5-6° C. or below) at the start of the reaction adds refrigeration costs to the operation. Previous attempts to synthesize propargyl bromide from phosphorus tribromide and propargyl alcohol in the absence of a base yielded large amounts of undesired side products; see L. Henry,
Chemische Berichte
, 1873, 6, 728.
It would be of considerable advantage if a way could be found of eliminating or at least significantly reducing formation of waxy solids in the process. It would be particularly advantageous if this could be done while avoiding the need for expensive refrigeration in the operation. An additional advantage would be the accomplishment of these things with a concomitant decrease in the formation of undesirable side products.
BRIEF SUMMARY OF THE INVENTION
This invention is deemed to enable achievement of the above advantages.
A feature of this invention is that propargyl bromide can be produced in good yield while minimizing the formation of undesired side products, such as 1,3-dibromopropene, 2,3-dibromopropene, and bromoallene. Surprisingly, this result can be achieved at higher addition temperatures than heretofore appreciated. And the process is economically advantageous, as a base such as pyridine or triethylamine is not required.
Provided by this invention is a process of producing propargyl bromide, which process comprises:
A) bringing together in a reaction zone under an inert atmosphere and in the absence of a base and in the presence of an inert diluent, a feed of phosphorus tribromide and a separate feed of propargyl alcohol thereby forming a reaction mixture;
B) while mechanically agitating the mixture being formed in A), maintaining the temperature of the mixture in the range of about 0° C. to about 25° C. to form a product mixture, and then
C) raising the temperature of the product mixture to a temperature in the range of about 40° C. to about 60° C. while stirring the product mixture for a ride period of at least about 2.5 hours.
Such process can be conducted as a batch process, as a semi-batch process, or as a continuous process.
Other embodiments and features of this invention will become still further apparent from the ensuing description and appended claims.
FURTHER DETAILED DESCRIPTION
When conducting a process in accordance with this invention there are basically two ways of bringing the reactants together in the reaction zone. One way is to feed the propargyl alcohol to the reaction zone and then feed the PBr
3
to the propargyl alcohol in the reaction zone. In such case, it matters not how or when the diluent is introduced into the reaction zone as long as at least sufficient diluent is present when the PBr
3
and propargyl alcohol are coming together in the reaction zone to serve as a heat sink for the heat of reaction evolved. Thus it is convenient to introduce all of the diluent before starting the feed of the PBr
3
, or to introduce a substantial portion of the diluent before starting the feed of the PBr
3
and to introduce additional diluent along with the feed of PBr
3
, either as a preformed solution of PBr
3
in the diluent, or as separate but concurrent feeds of PBr
3
and of diluent.
The second way of bringing the reactants together in the reaction zone is to feed propargyl alcohol and PBr
3
separately but concurrently into the reaction zone. Here again it matters not how or when the diluent is introduced into the reaction zone as long as at least sufficient diluent is present to serve as a heat sink for the heat of reaction evolved when the PBr
3
and propargyl alcohol are coming together in the reaction zone. For example, all of the diluent can be introduced into the reaction zone before starting the separate but concurrent feeds of the PBr
3
and of the propargyl alcohol. Alternatively, a substantial portion of the diluent can be introduced into the reaction zone before starting the concurrent feeds and additional diluent can accompany either or both such concurrent feeds. In other words, additional diluent maybe introduced as a preformed solution of PBr
3
in the diluent, as a preformed solution of propargyl alcohol in the diluent, and/or as a separate but concurrent feed with the concurrent feeds of PBr
3
and of propargyl alcohol.
In any event, the point at which the propargyl alcohol and the phosphorus tribromide come into contact with each other is part of the reaction zone. Preferably, the reactants are concurrently fed into a reaction zone composed of at least one reactor in which all of the components—whether fed individually or in any subcombination(s)—all come together for the first time and in which the process is initiated and carried out.
When the propargyl alcohol and the phosphorus tribromide come into contact with each other, the mechanical agitation can be accomplished by the use of, for example,jet mixers or static mixers. Optionally, high shear mechanical agitation and/or high speed jet dip legs may also be used.
The use of the term “concurrent” does not exclude the possibility of inconsequential interruptions taking place during the feeds. Nor does this term imply that the feeds must start at exactly the same moment in time. In the case of a co-feed process, the two feeds can be initiated with an interval of time between such initiation as long as the interval is sufficiently short as to cause no material adverse effect upon the overall process. Likewise in the case of a tri-feed or multi-feed operation, there maybe one or two different time intervals between or among the respective feeds, again provided that the time intervals are of sufficiently short duration to cause no material adverse effect upon the overall process.
The processes of this invention, whether performed in a batch mode, semi-batch (semi-continuous) mode, or continuous mode, are preferably conducted so that such things as the feeds, reaction, and maintenance of the desired temperature occur “continuously” during the reaction. However, it cannot be stressed strongly enough that one must not gain the impression that inconsequential interruption in one or more of such things cannot occur. Interruptions which do not materially affect the conduct of the process are not excluded from the scope of this invention. Whatever the terms used, the process should be conducted as one of ordinary skill in the art would carry out the processes after a thorough, unbiased reading of this entire disclosure and in keeping with the spirit of the invention gained from such a reading.
As is well known in the art, operation under an inert atmosphere requires the presence of an inert gas such as nitrogen, argon, or helium. This minimizes or excludes oxygen from the reaction zone. Nitrogen is a preferred inert gas in the practice of this invention. The inert gas can be introduced into the reaction zone by various means, such as sweeping the reaction zone with an inert gas prior to the introduction of the inert diluent, or passing the inert gas into the reaction zone during the process.
The inert diluent used is typically one or more (i) paraffinic hydrocarbons, (ii) cycloparaffinic hydrocarbons, or (iii) aromatic hydrocarbons or a mixture of any two or all three of (i), (ii) and (iii), but can be any inert liquid, i.e., a liquid which does not react with either the reactants or the products produced in the reaction in such a way
Elnager Hassan Y.
Herndon, Jr. Robert C.
Mero Christopher L.
Albemarle Corporation
Price Elvis O.
Spielman, Jr. Edgar E.
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