Butyl carbamate

Adsorption / desorption

Link to relevant study record(s)

Reference

Endpoint:

adsorption / desorption, other

Remarks:

Adsorption estimated

Type of information:

(Q)SAR

Remarks:

Data estimated by KOCWIN v2.00 (EPISuite v 4.1)

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification

Justification for type of information:

See below under 'Overall remarks, attachments' for applicability domain.

Qualifier:

according to guideline

Guideline:

other: REACH guidance on QSARs: Chapter R.6. QSARs and grouping of chemicals

Principles of method if other than guideline:

The Koc value of the test substance was estimated using MCI (molecular connectivity index) as well as Kow methods of KOCWIN v.2.00 program of EPISuite (v.4.1).

Specific details on test material used for the study:

Input data for the model:
CAS: 592-35-8; or
SMILES: O=C(OCCCC)N

Computational methods:

The Koc value of the test substance was estimated using MCI (molecular connectivity index) as well as Kow methods of KOCWIN v.2.00 program of EPISuite (v.4.1).
 
(1) Estimations using Molecular Connectivity Index:
The equation derived by the non-polar (no correction factor) regression is:
  log Koc  =  0.5213 MCI  +  0.60
  (n = 69, r2 = 0.967, std dev = 0.247, avg dev = 0.199)
for comparison, the previous version of PCKOCWIN used a very similar equation:
 log Koc  =  0.53 MCI  +  0.62
Adding in the correction factor regression yields the final MCI equation:
 log Koc  =  0.5213 MCI  +  0.60 + ΣPfN  

where ΣPfN is the summation of the products of all applicable correction factor coefficients from Appendix D multiplied by the number of times (N) that factor is counted for the structure. 

(2) Estimations Using Log Kow:
A traditional method of estimating soil adsorption Koc involves correlations developed with log octanol-water partition coefficient (log Kow) (Doucette, 2000).  Since an expanded experimental Koc database was available from the new MCI regression, it was decided to develop a log Kow estimation methodology that was potentially more accurate than existing log Kow QSARs for diverse structure datasets.
Effectively, the new log Kow methodology simply replaces the MCI descriptor with log Kow and derives similar equations.  The derivation uses the same training and validation data sets.  The training set is divided into the same non-polar (no correction factors) and correction factor sets.  The same correction factors are also used.
Separate equations correlating log Koc with log Kow were derived for nonpolar and polar compounds because it was statistically more accurate to do so than to use the approach taken with the MCI-based method.  The equation derived by the non-polar (no correction factor) regression is:
 log Koc  =  0.8679 Log Kow  -  0.0004
    (n = 68, r2 = 0.877, std dev = 0.478, avg dev = 0.371)

One non-polar compound was removed from the regression (hexabromobiphenyl) because it was the only compound without a recommended experimental log Kow and the accuracy of its estimated log Kow (9.10) is suspect.  This equation is used for any compound having no correction factors.

For the multiple-linear regression using correction factors, log Kow was included as an individual descriptor.  For compounds having correction factors, the equation is:
 log Koc  =  0.55313 Log Kow  +  0.9251 + ΣPfN  
where ΣPfN is the summation of the products of all applicable correction factor coefficients from Appendix D multiplied by the number of times (N) that factor is counted for the structure.

Key result

Type:

Koc

Remarks:

(estimated)

Value:

40.27 L/kg

Remarks on result:

other: log Koc:1.6; based on MCI method of KOCWIN v.2.0

Key result

Type:

Koc

Remarks:

(estimated)

Value:

20.55 L/kg

Remarks on result:

other: log Koc: 1.3; based on Kow method of KOCWIN v.2.0

Adsorption and desorption constants:

Estimated Koc from KOCWIN v.2.0 of EPISuite:
SMILES : O=C(OCCCC)N
CHEM : Carbamic acid, butyl ester
MOL FOR: C5 H11 N1 O2
MOL WT : 117.15
--------------------------- KOCWIN v2.00 Results ---------------------------

Koc Estimate from MCI:
---------------------
First Order Molecular Connectivity Index ........... : 3.770
Non-Corrected Log Koc (0.5213 MCI + 0.60) .......... : 2.5651
Fragment Correction(s):
1 Carbamate (N-CO-O) or (N-CO-S) ....... : -0.9601
Corrected Log Koc .................................. : 1.6050

Estimated Koc: 40.27 L/kg <===========

Koc Estimate from Log Kow:
-------------------------
Log Kow (experimental DB) ......................... : 0.85
Non-Corrected Log Koc (0.55313 logKow + 0.9251) .... : 1.3953
Fragment Correction(s):
1 Carbamate (N-CO-O) or (N-CO-S) ....... : -0.0825
Corrected Log Koc .................................. : 1.3127

Estimated Koc: 20.55 L/kg <===========

Conclusions:

The estimated Koc value of the test substance based on Kow and MCI methods of KOCWIN v.2.0 were determined to be 20.55 and 40.27 L/kg respectively.

Executive summary:

The Koc was estimated using the Kow and MCI (molecular connectivity index) methods of KOCWIN v2.00 program (EPIWEB v4.1). CAS number was used as the input parameterl.The estimated Koc value of the the test substance based on Kow and MCI methods of KOCWIN v.2.0 were determined to be 20.55 L/kg (log Koc = 1.3) and 40.27 L/kg (log Koc = 1.6) respectively(US EPA, 2016). This is indicative of high mobility or low adsorption potential to organic matter (White, 2009).

Description of key information

The estimated Koc value of the SoI using KOCWIN v.2.00 was determined to be 20.55 L/kg (based on Kow) and 40.27 L/kg (based on MCI).

Key value for chemical safety assessment

Koc at 20 °C:

20.55

Additional information

Adsorption potential (Koc) is expected to be low due to ≤3 log Kow value of the test substance. Nevertheless, a adsorption coefficient (Koc) value has been estimated using the KOCWIN program of EPISuite to allow a risk assessment of soil and sediment compartments..

The Koc was estimated using the Kow and MCI (molecular connectivity index) methods of KOCWIN v2.00 program (EPISuite v4.1). CAS number was used as the input parameter.The estimated Koc value of the test substance based on Kow and MCI methods of KOCWIN v.2.0 were determined to be 20.55 L/kg (log Koc = 1.3) and 40.27 L/kg (log Koc = 1.6) respectively (US EPA, 2016). This is indicative of high mobility or low adsorption potential to organic matter (White, 2009).

[LogKoc: 1.3]