Chemistry Reference
In-Depth Information
Tab. 3.3.
Vapor pressures of phosgene and some important substitutes [15-19].
Phosgenation reagent
Vapor pressure
(Pa)
Vapor pressure
(Torr)
Temp.
(˚C)
Ref.
Phosgene
162000
1215
20
15
Diphosgene
1370
10.3
20
16
Triphosgene
20
0.15
20
16
Diethyl carbonate
1100
8.3
20
15
Dimethyl carbonate
13300
100
37
17
Acetic anhydride
500
3.8
20
15
Triflic anhydride
1060
8
20
18
Phosphoryl chloride
5300
40
27
15
Thionyl chloride
12900
97
20
19
has also been synthesized independently and characterized by the APCI-MS tech-
nique.
3.3
Physical Properties
Phosgene equivalents are gaseous, liquid or solid compounds. The main physical
properties of phosgene and some phosgene equivalents are presented in Table 3.2.
The potential danger in the handling of the phosgene equivalents is associated
with the vapor pressures of the compounds. Very few specific data are available. In
the case of the chlorinated phosgene substitutes, diphosgene and triphosgene, the
vapor pressures are significantly lower and a value as low as 0.15 Torr has been
reported for triphosgene (Table 3.3).
3.4
Physiological Data
While searching for significant data to describe the potential workplace health
hazards associated with the use of phosgene equivalents, we were surprised by the
lack of quantitative data for monitoring exposure to these compounds. The reason
for this is definitely the still limited use of phosgene equivalents in industrial pro-
cesses. The best approach to prevent erroneous and hazardous use of these mate-
rials is to first gain thorough knowledge of the material data sheets, which are easily
accessible and available [18]. Some threshold limit value/time-weighted average (TLV-
TWA) data are collected in Table 3.4. The class representative, phosgene, has a TLV
of 0.1 ppm, but other phosgene equivalents have values ranging from 0.005 ppm
(hexamethylene diisocyanate) to 5000 ppm (carbon dioxide). It should be noted
that aliphatic isocyanates have even lower TLVs and that suitable safety measures
have to be taken before working with these reagents [20].
