Phthalic anhydride

Phototransformation in water

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Reason / purpose for cross-reference:

read-across: supporting information

Study type:

direct photolysis

Principles of method if other than guideline:

A photochemical air-cooled reactor, using a medium-power mercury arc lamp for oxidation of organic matter in sea water

GLP compliance:

no

Radiolabelling:

no

Light source:

other: 380 W mercury lamp

% Degr.:

50

Sampling time:

0.93 h

Test condition:

sea water

Transformation products:

not measured

First order rate constant (hours E-1) for photooxidation in sea water
 was  0.75. That is equivalent with a half-life of  0.93 hours.

Executive summary:

In an irradiation experiment a first order rate constant (k/hour) for photooxidation in sea water was determined to be 0.75. That is equivalent with a half-life of 0.93 hours (Armstrong, 1968).

Reference 2

Endpoint:

phototransformation in water

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Basic data given

Study type:

direct photolysis

Principles of method if other than guideline:

Method: Photochemical transformations of phthalic anhydride in various aquatic media

GLP compliance:

not specified

Analytical method:

other: GC, HPLC and gel permeation chromatography

Light source:

other: mercury lamp and sunlight

Light spectrum: wavelength in nm:

365 - 366

DT50:

3.9 h

Test condition:

distilled water

DT50:

6.3 h

Test condition:

riverine water

DT50:

9.6 h

Test condition:

sea water

DT50:

6.8 h

Test condition:

artificial sea water

Transformation products:

yes

No.:

#1

Degradation products (CAS No./EC No./EINECS Name): polyphenyl
RS-Freetext:
Phthalic anhydride hydrolyzed to phthalic acid. Small quantities of  
benzoic acid were found. Polyphenyl (1,4´-bonds dominating) with a  
molecular weight of predominantly 2800 - 3600 g/mol was formed by  
decarboxylation of phthalic acid under anaerobic conditions. The half-lives
of phthalic anhydride were 3.9 h (distilled water), 6.3 h (riverine water), 6.8 h (artificial sea water), and 
9.6 h (natural sea water) under  anaerobic conditions. 
It was assumed that the retardation of  photodegradation of phthalic acid
 in sea water and river water was due to  halides and humic compounds
The results of the experiments on phthalic anhydride solution in distilled water
 in sunlight showed a very slow rate. In 15 days exposure only abot 4% of the 
reactant was transformed.
 

Executive summary:

Experiments on photochemical transformations of phthalic anhydride in various aquatic media were conducted in a photochemical reactor and in natural sunlight (Bajt, 1992). The photochemical reactions of phthalic anhydride, which hydrolyses to phthalic acid in water, showed polymerisation to polyphenyl. Kinetic studies of photochemical transformations of phthalic anhydride in all aqueous media revealed the occurrence of first order reactions with different rate constants.

The half-lives of phthalic anhydride were 3.9 h (distilled water), 
6.3 h (riverine water), 6.8 h (artificial sea water), and  
9.6 h (natural sea water) under  anaerobic conditions.

.

Description of key information

In the hydrosphere, phthalic anhydrid is transformed photochemically under anaerobic conditions showing polymerisation to polyphenyl. The half-lifes are in the range from 3.9 h to 9.6 h following first oder reactions. For photooxidation in sea water a half-life of 0.93 hours is obtained (Armstrong, 1968; Bajt, 1992).

Additional information

Experiments on photochemical transformations of phthalic anhydride in various aquatic media were conducted in a photochemical reactor and in natural sunlight (Bajt, 1992). The photochemical reactions of phthalic anhydride, which hydrolyses to phthalic acid in water, showed polymerisation to polyphenyl. Kinetic studies of photochemical transformations of phthalic anhydride in all aqueous media revealed the occurrence of first order reactions with different rate constants. The half-lives of phthalic anhydride were 3.9 h (distilled water), 6.3 h (riverine water), 6.8 h (artificial sea water), and 9.6 h (natural sea water) under anaerobic conditions. In an irradiation experiment with phthalic acid, the hydrolysis product of phthalic anhydride, a first order rate constant (k/hours ) for photooxidation in sea water was determined to be 0.75. That is equivalent with a half-life of 0.93 hours (Armstrong, 1968).