Zinc bis(2-ethylhexanoate)

Vapour pressure

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

vapour pressure

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reference 2

Endpoint:

vapour pressure

Type of information:

other: handbook data

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Qualifier:

no guideline followed

Principles of method if other than guideline:

not applicable for handbook data or calculation method

Temp.:

25 °C

Vapour pressure:

0.043 mm Hg

Remarks on result:

other: handbook data

Temp.:

25 °C

Vapour pressure:

0.278 mm Hg

Remarks on result:

other: EPI Suite estimation: Mean of Antoine & Grain method

Conclusions:

MPBPVP™, Mean VP of Antoine and Grain method; EPI Suite™ stated the following experimental determined and estimated vapour pressures for hexanoic acid (CAS # 142-62-1) at 25 °C: exp. database: 0.0435 mm Hg (5.08 Pa); estimate: 0.278 mm Hg (37.1 Pa).

Description of key information

The vapour pressure of a substance is defined as the saturation pressure above a solid or liquid substance. In EU method A.4, seven different measuring methods are listed for the measurement of the vapour pressure of solids and liquids. However, the vapour pressure does not need to be measured due to technical reasons if calculations indicate that the value is significantly less than 10^-5 Pa. Zinc bis(2-ethylhexanoate) is a clear, highly viscous liquid (salts of an organic acid and an inorganic cation). In view of this, the volatility of this substance can therefore be safely assumed to be negligible, i.e. below the level of significance (10^-5 Pa). For purposes of comparison, an atom fragment contribution method (MPBPVP™, Mean VP of Antoine and Grain method; EPI Suite™) stated following experimental determined and estimated vapour pressures for the fatty acid at 25 °C (please refer to the respective study record):

C6: hexanoic acid (CAS # 142-62-1):

- experimental database: 0.0435 mm Hg (0.22 Pa)

- estimate: 0.278 mm Hg (37.1 Pa)

Since the vapour pressure of a substance depends among others on the chemical structure and decreases with increasing inter- and intramolecular interactions. An ionic compound such as zinc bis(2-ethylhexanoate) shows a higher strength of attraction, because of the electrostatic interaction between its positive and negative ions. This ionic interaction leads to a higher lattice energy compared with the van-der-Waals interaction of the uncharged fatty acid and consequently to a much lower vapour pressure. Based on the above, the vapour pressure of zinc bis(2-ethylhexanoate) is considered to be negligible based on the fact that

(i) the vapour pressure of the corresponding acid is already very low (see above) and

(ii) the vapour pressure of the corresponding ionic species is considered to be magnitudes lower since the ionic bond strength is higher compared to the Van-der-Waals interactions of the uncharged molecule.

In consideration of the ionic nature of this compound, it can therefore be anticipated that the vapour pressure of zinc bis(2-ethylhexanoate) is well below the value for the organic acid, and thus negligible. Therefore, in accordance with Regulation (EC) No 1907/2006, Annex XI, Section 1.2, testing does not need to be conducted.