Registration Dossier

Administrative data

Endpoint:
phototransformation in air
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Submittet for publication: 2009-11-13
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No GLP compliance, no guideline followed

Data source

Reference
Reference Type:
publication
Title:
Unnamed
Year:
2010

Materials and methods

Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Rate coefficients at room temperature for the reaction of 2-ethyl-1-hexanol with OH and NO3 radicals and with Cl atoms have been determined in a 150 L PTFE chamber using GC-FID/SPME and FTIR as detection systems. Rate coefficients for the reaction of 2-ethyl-1-hexanol with OH and NO3 radicals and with Cl
atoms at 298 2 K were determined using a relative rate method. In this technique the disappearance of the substrate 2-ethyl-1-hexanol due to reaction with the reactive species (OH, NO3 or Cl) is measured relative to that of a reference compound, the rate coefficient of which with the reactive species is reliable known. The decay of the substrate from [S]0 at time t = 0 to [S]t at time t, and the simultaneous loss of the reference compound from an initial concentration of [R]0 to [R]t at time t is given by the following equation:
ln([S]0/[S]t) = (kS/kR)*ln([R]0/[R]t)
Thus, a plot of {ln[S]0/[S]t} versus {ln[R]0/[R]t} should be a straight line passing through the origin and the slope gives the ratio of rate coefficients kS/kR.
Quantificaqtion was against the internal standard benzene (low rate coefficients with OH, NO3 and Cl). Each reaction studied was measured relative to the reaction of two reference standards. The decay of the reactant, reference compound and internal standard were monitored by gas chromatography with flame ionization detection (GC-FID, Shimadzu 14A) using a capillary column (30 m 0.32 mm 1 µm, TRACSIL TRB-1701, TEKNOKROMA) of intermediate polarity. All organics were subjected to radiation alone to ensure that photolysis was negligible in all cases and to confirm that unrecognized reactions did not occur in the absence of OH, NO3 or chlorine atom sources.
To test for dark reactions, the precursor of the radical and the organics were kept in the reactor for a certain period of time (8 h) in the absence of photolysis and no significant variation of the chromatographic areas was obtained. The occurrence of secondary chemistry was ruled out on the basis of experiments with different concentrations of the reference and the alcohol which showed consistency in the slopes in all cases (with intercepts at zero). Finally, for each organics
mixture a number of injections (typically 12 or more) of the unreacted mixture was carried out to obtain an estimate of the precision associated with the measurements for use in error analysis. The reproducibility of these measurements also included losses due to the walls of the reaction bag, and it was found that wall losses were not significant.
Using methyl nitrite as OH radical precuser, UV radation with a maximum at 360 nm was used, using H2O2 as OH radical precuser, emission maximum was at 254 nm.
GLP compliance:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
Purity of 2-ethyl-1-hexanol: 99%

Study design

Light source:
other: 4 fluorescent lamps, type Philips TUV G13 36W
Light spectrum: wavelength in nm:
>= 254 - <= 360

Results and discussion

Any other information on results incl. tables

Relative and absolute rate coefficients (k in units of cm^3 molecule^(-1) s^(-1)) for the reaction of 2-ethyl-1-hexanol with OH and NO3 radicals and Cl atoms, and for the reaction of n-butanol with NO3 radical. From the results it was concluded that CH3ONO cannot be used as a precurser for OH radicals in combination with the SPME-FID detection method (but very well for FTIR detection). Therefore, results are given in the tabel but were not used for determination of the rate coefficient.

Reaction

Reference compound

kS/kR(± 2σ)

kS(±2σ)

2-Ethyl-1-hexanol + OH

Cyclohexane

1.203±0.04

(0.84±0.30)x10-11

(CH3ONO as precursor)

Octanol

0.952±0.03

(1.37±0.14)x10-11

2-Ethyl-1-hexanol + OH

Cyclohexane

1.621±0.044

(1.13±0.12)x10-11

(H2O2as precursor)

Octanol

0.645±0.0

(0.93±0.09)x10-11

2-Ethyl-1-hexanol + OH

Propene

0.474±0.008

(1.22±0.02)x10-11

(CH3ONO as precursor and FTIR)

Ethene

1.457±0.031

(1.24±0.08)x10-11

n-Butanol + NO3

Methacrolein

0.950±0.41

(3.14±0.97)x10-15

2-Ethyl-1-hexanol + NO3

Butanol

0.940±0.04

(2.95±0.92)x10-15

 

Methacrolein

0.926±0.06

(2.91±0.92)x10-15

2-Ethyl-1-hexanol + Cl

Cyclohexane

0.633±0.03

(1.94±0.28)x10-10

 

Furan

0.911±0.06

(1.82±0.22)x10-10

Applicant's summary and conclusion

Validity criteria fulfilled:
not applicable
Conclusions:
Rate coefficients at room temperature for the reactions of 2-ethyl-1-hexanol with OH and NO3 radicals and with Cl atoms, clearly indicate that reaction with OH is the most relevant degradation process for this compound in the atmosphere. In this case a rate constant of 1.13 x 10^(-11) cm^3/(molecule x s) and an atmospheric lifetime of 24.6 h was determined. The determined rate coefficients are consistent with the expected reactivity given the chemical structure of this compound.