Chemistry Reference
In-Depth Information
diameter 1.6 cm), containing the aforementioned amounts of triphosgene and a
bead of catalyst, sealed by a cap. This serves as a storage vessel. Before use, the cap
is removed and the cartridge and reaction vessel are connected by a length of tub-
ing with a gas-tight adapter. A dosimeter badge and paper for measuring phosgene
dosage are also supplied. The cartridges are commercially available from Sigma-
Aldrich [8] (Table 7.2). Instructions for their use are given in [2, 8] and can be
retrieved from [2].
7.1.2.4
In situ Phosgene Source
The requisite amount of triphosgene to generate the desired amount of phosgene
is placed in the reaction vessel, together with the catalyst for the ''depolymeriza-
tion'' [1, 2, 5], the other reactants and reagents, and the solvent. (In contrast to
solid triphosgene, in solution it is decomposed by the catalyst even at temperatures
below its mp). As above, phosgene is released over a defined period. In the pres-
ence of certain nucleophiles, particularly certain amines (as reactants or scav-
engers), the phosgene might be released all at once. If this were the case, the
method would operate as a usual phosgenation reaction, but the safety aspect of
safety phosgenation would be somewhat reduced. Nevertheless, the method is ad-
vantageous in terms of its simple handling.
7.2
Sources of Phosgenation Reagents
Available phosgenation reagents for laboratory use are listed in Table 7.2. Some are
commercially available, while preparative procedures for others are either given in
the relevant section of Chapter 4 in this topic, or in the literature. For the struc-
tures of all these phosgenation reagents, see Scheme 2.1, Chapter 2.
Phosgene can be obtained on a large scale from Van De Mark (now part of
SNPE), located in Lockport, N.Y., who sell the gas on the merchant market.
Diphosgene can be obtained on a large scale from Degussa, UK, Dona Fine
Chemicals, Poland, Fabricolor Vus, US, Fine Organics, UK, Ubichem, UK and Hun-
gary, VUOS, Czech Republic, or Vujin Organic Chemical Plant, PR China.
Triphosgene can be obtained on a large scale from Dr. Eckert GmbH [2], Ger-
many, Ubichem, UK and Hungary, or Synergetica, PR China/US.
7.3
Safety Precautions
The high toxicity of phosgene and several of its substitutes, as well as of some
products (!) from phosgenation reactions such as alkyl isocyanates (see Table 3.4,
Section 3.4), necessitates restrictive regulations about exposure to them. In this
section, instructions are given with a view to obtaining maximum benefit from
these synthetically highly valuable reagents with a minimum of hazard. A general
