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EC number: 200-830-5 | CAS number: 75-00-3
- Life Cycle description
- Uses advised against
- Endpoint summary
- Appearance / physical state / colour
- Melting point / freezing point
- Boiling point
- Density
- Particle size distribution (Granulometry)
- Vapour pressure
- Partition coefficient
- Water solubility
- Solubility in organic solvents / fat solubility
- Surface tension
- Flash point
- Auto flammability
- Flammability
- Explosiveness
- Oxidising properties
- Oxidation reduction potential
- Stability in organic solvents and identity of relevant degradation products
- Storage stability and reactivity towards container material
- Stability: thermal, sunlight, metals
- pH
- Dissociation constant
- Viscosity
- Additional physico-chemical information
- Additional physico-chemical properties of nanomaterials
- Nanomaterial agglomeration / aggregation
- Nanomaterial crystalline phase
- Nanomaterial crystallite and grain size
- Nanomaterial aspect ratio / shape
- Nanomaterial specific surface area
- Nanomaterial Zeta potential
- Nanomaterial surface chemistry
- Nanomaterial dustiness
- Nanomaterial porosity
- Nanomaterial pour density
- Nanomaterial photocatalytic activity
- Nanomaterial radical formation potential
- Nanomaterial catalytic activity
- Endpoint summary
- Stability
- Biodegradation
- Bioaccumulation
- Transport and distribution
- Environmental data
- Additional information on environmental fate and behaviour
- Ecotoxicological Summary
- Aquatic toxicity
- Endpoint summary
- Short-term toxicity to fish
- Long-term toxicity to fish
- Short-term toxicity to aquatic invertebrates
- Long-term toxicity to aquatic invertebrates
- Toxicity to aquatic algae and cyanobacteria
- Toxicity to aquatic plants other than algae
- Toxicity to microorganisms
- Endocrine disrupter testing in aquatic vertebrates – in vivo
- Toxicity to other aquatic organisms
- Sediment toxicity
- Terrestrial toxicity
- Biological effects monitoring
- Biotransformation and kinetics
- Additional ecotoxological information
- Toxicological Summary
- Toxicokinetics, metabolism and distribution
- Acute Toxicity
- Irritation / corrosion
- Sensitisation
- Repeated dose toxicity
- Genetic toxicity
- Carcinogenicity
- Toxicity to reproduction
- Specific investigations
- Exposure related observations in humans
- Toxic effects on livestock and pets
- Additional toxicological data
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Hydrolysis
Administrative data
Link to relevant study record(s)
- Endpoint:
- hydrolysis
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Acceptable, well documented publication which meets basic scientific principles (peer reviewed in OECD-SIDS)
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Experimental data
- GLP compliance:
- no
- Radiolabelling:
- no
- Analytical monitoring:
- yes
- Details on sampling:
- GC-MS
- Transformation products:
- not measured
- pH:
- 7
- Temp.:
- 25 °C
- Hydrolysis rate constant:
- ca. 0 min-1
- DT50:
- 2.6 yr
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: r2 >=0.9
- Validity criteria fulfilled:
- not applicable
- Conclusions:
- The neutral reaction rate constant for the hydrolysis of chloroethane is 5.1 x 10-7, resulting in an estimated half-life of 2.6 years.
- Executive summary:
Jeffers and Wolfe (1996) determined both the neutral and alkaline reaction rates for the hydrolysis of chloroethane. The neutral reaction measured in 0.01 M hydrochloric acid at 25 °C was found to predominate, with a rate constant of 5.1 x 10-7 min-1, resulting in an estimated half-life for chloroethane of 2.6 years.
- Endpoint:
- hydrolysis
- Type of information:
- experimental study
- Adequacy of study:
- weight of evidence
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Acceptable, well documented publication which meets basic scientific principles (peer reviewed in OECD-SIDS)
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Literature review
- GLP compliance:
- no
- Radiolabelling:
- no
- Analytical monitoring:
- no
- Estimation method (if used):
- Kinetic based calculations
- Transformation products:
- not specified
- pH:
- 7
- Temp.:
- 25 °C
- Hydrolysis rate constant:
- 0 s-1
- DT50:
- 38 d
- Type:
- (pseudo-)first order (= half-life)
- Remarks on result:
- other: 38 d also at pH 4 and 9
- Validity criteria fulfilled:
- not applicable
- Conclusions:
- The hydrolytic half-life in water at 25 °C and pH 4, 7 and 9 was estimated to be 38 days.
- Executive summary:
In their critical review of hydrolysis of organic compounds in water under environmental conditions Mabey and Mill (1978) examined the rate constants for hydrolysis in water of 12 classes of organic compounds. The objective of their work was to use available data to estimate the persistence of these compounds in freshwater systems. For ethylchloride experimental data at 100 °C are available, from which the authors extrapolated the hydrolytic half-life of 38 days in water at 25 °C and pH 4 - 9. The hydrolysis rate constant is 2.10e-07 s-1.
- Endpoint:
- hydrolysis
- Type of information:
- experimental study
- Adequacy of study:
- supporting study
- Reliability:
- 2 (reliable with restrictions)
- Rationale for reliability incl. deficiencies:
- other: Acceptable, well documented publication which meets basic scientific principles (peer reviewed)
- Qualifier:
- no guideline followed
- Principles of method if other than guideline:
- Literature review
- GLP compliance:
- no
- Radiolabelling:
- no
- Estimation method (if used):
- Literature review
- Transformation products:
- not measured
- pH:
- 5.6
- Temp.:
- 25 °C
- Hydrolysis rate constant:
- 0 min-1
- DT50:
- 2.54 yr
- Type:
- (pseudo-)first order (= half-life)
- pH:
- 7
- Temp.:
- 25 °C
- Hydrolysis rate constant:
- 0 min-1
- DT50:
- 2.54 yr
- Type:
- (pseudo-)first order (= half-life)
- pH:
- 5.6
- Temp.:
- 10 °C
- Hydrolysis rate constant:
- 0 min-1
- DT50:
- 27.2 yr
- pH:
- 7
- Temp.:
- 10 °C
- Hydrolysis rate constant:
- 0 min-1
- DT50:
- 27.2 yr
- Validity criteria fulfilled:
- not applicable
- Conclusions:
- For chloroethane the rate constant in water at 25 °C and pH 7 is 5.18 x 10-7, and the hydrolytic half-lie is 2.54 years.
- Executive summary:
Washington (1995) reports in his review Arrhenius parameters for chloroethane for pseudo-first order rate constants for base (Kb) and neutral (Kn) reactions (data provided under “Any other information on results incl. tables”). Further, the review shows pseudo-first order hydrolysis rate constants describing the observed rate of substrate consumption (Kobs) at pH 7 and pH 5.6, each at 25°C (“environmentally relevant value”) and at 10°C (lower bound temperature for deep ground water):
25 °C Data:
pH 7: Kobs = 5.18E-07; t1/2= 2.54 yr
pH 5.6: Kobs = 5.18E-07; t1/2= 2.54 yr
10 °C Data:
pH 7: Kobs = 4.84E-08; t1/2= 27.2 yr
pH 5.6: Kobs = 4.84E-08; t1/2= 27.2 yr
Referenceopen allclose all
1. The Arrhenius parameters for both the neutral and alkaline reactions are presented in the table below:
Table: Arrhenius parameters for ethyl chloride for the neutral and alkaline reactions
|
A (L mol-1 min-1) |
E (kJ/mol) |
K (25°C, pH 7) |
t1/2** |
Arrhenius parameters for the neutral reaction* |
(1.4 ± 0.3) x 1013 |
110.8 ± 3.8 |
Kn= 5.1 x 10-7 |
2.6 years |
Arrhenius parameters for the alkaline reaction**
|
(3.7 ± 0.8) x 1013 |
101.2 ± 10.2 |
Kb= 6.7 x 10-12 |
- |
* ‘‘Neutral’’ hydrolysis carried out in solutions of 0.01 M HCl
** Alkaline hydrolysis measured in NaOH solutions ranging from 0.1 to 0.001 M NaOH. The alkaline hydrolysis half-life is determined by the “neutral” reaction.
Based on the results, a brominated compound is more reactive than its chlorinated analogue by a factor of 10 to 100, by both neutral and alkaline reaction mechanisms. Greater reactivity of Br versus Cl compounds is due to lower activation energy and entropy effects that also contribute in the same direction. Within a series of halogenated compounds, the order of reactivity is identical for brominated and chlorinated analogues. Substitution of F for Cl in the ethanes causes an enormous drop in neutral hydrolysis.
1. Hydrolysis kinetic
Overall hydrolysis is a transformation of an organic chemical with water, resulting in the formation of a new covalent bond with OH. The overall reaction may be summarized as
R-X + H2O → R-OH + HX
X represents a good leaving group (an atom much more electronegative that carbon, e.g. Cl). The detailed mechanism may involve a protonated or anionic intermediate or a carbonium ion, or any combination of these intermediates. But whatever the mechanism, the rate law for hydrolysis of substrate RX usually can be put in the form
-d[RX]/dt = KH [RX] = KB [OH-][RX] + KA [H+][RX] + KN’ [H2O] [RX] (1)
Where KA, KB and KN are the second-order rate constants for acid and base catalysed and neutral processes, respectively. In water is the KN’ [H2O] a constant (KN). KH is the observed or estimated rate constant for hydrolysis at constant pH. Equation (1) assumes that the individual rate processes for the acid, base and neutral hydrolysis obey first-order kinetics with the hydrolysable chemical, RX, it is possible to write the following equation for KH:
KH = KB [OH-] + KA [H+] + KN (2)
From the equilibrium term for the ionisation of water, KW:
KW = [H+] [OH-] = 1 x 10 -14 (3)
It is possible to substitute for [OH-] in the equation (2), giving
KH = KB ∙ KW / [H+] + KA [H+] + KN (4)
Because KH is a pseudo first-order rate constant at a fixed pH, the half-life of hydrolysis can be calculated as below:
t1/2 = ln2 / KH = 0.693 / KH (5)
pH Dependence:
From the equation (5) it is evident how pH affects the overall rate constant for hydrolysis, KH: at high or low pH (high OH- or H+) either base or acid catalysed term is usually dominant, while at pH 7 the neutral processes can often be the most important. However, the detailed relationship of pH and rate depends on the specific values of KA, KB and KN.
The typical log KH vs. pH can be plotted to demonstrate for the chemicals which undergo acid, water and base catalysed hydrolysis at a specific pH with a curve composited of three straight lines with slops +1, 0 and -1 respectively as below:
(a) log KH = log (KB ∙ KW ) + pH
(b) log KH = log KN
(c) log KH = log KA – pH
Most log KH vs. pH curves are found to have one or two intercepts corresponding to pH values where two kinds of rate processes contribute equally to the overall process. Thus in Figure 1 of the publication (see Mabey and Mill, 1978) the intercept IAN corresponds to a pH value where KA [H+] = KN, similarly, IBN corresponds to KB [OH-] = KN. In cases where KA, KB or KN = 0, only one intercept is observed. Values of pH corresponding to the I may be calculated readily from the values of KA, KB and KN as below:
IAN = - log (KN / KA) (6)
INB = - log (KB ∙ KW / KN) (7)
IAB = - [log (KB ∙ KW / KA)] / 2 (8)
Use of intercepts in tabulating dat on rates of hydrolysis as a function of pH greatly simplifies the task of estimating the effect of pH on the rate constant KH for a specific compound.
2. Rate constants for Chloroethane
Chloraethane hydrolyses in water by neutral and base catalysed reaction to given ethanol and hydrogen chloride. The hydrochloric acid formed dissociates at the neutral pH of most natural waters and forms a chloride salt. No acid catalysed processes observed.
The rate constant of 1.x 10-4 by neutral and base catalysed reaction was reported for chloraethane at 100.2 °C. Rate constants of KN for hydrolysis reaction at 25 °C and pH was extrapolated based on the experimental rate constant and the temperature coefficient.
3. Hydrolysis as a function of pH for Chloroethane
The intercepts I, corresponding to pH values where two rate processes contribute equally to the observed rate constants, KN and KB for several primary alkyl halides are listed in the table below:
Organic halides KN s-1 KB [OH-] s-1 INB*
MeF 7.44 x 10-10 5.82 x 10-14 11.1
MeCl 2.37 x 10-8 6.18 x 10-13 11.6
MeBr 4.09 x 10-7 1.41 x 10-11 11.5
MeI 7.28 x 10-8 6.47 x 10-12 11.0
CH2CHCH2Cl 1.16 x 10-7 6.42 x 10-12 11.3
C6H5CH2Cl 1.28 x 10-5 > 13
*These values were calculated from the equations (6), (7) and (8).
The intercepts INB lying above pH 11 indicate that neutral hydrolysis rate term for these compounds will dominate over typical environmental pH values of 4 to 9. Only above pH 11 will the base catalysed rate term contribute to the overall hydrolysis rate term. Likewise, hydrolysis of chloroethane is considerd not to be affected by pH values ranged from 4 to 9.
Kinetic parameters for hydrolysis of chloroethane based on the data of Jeffers and Wolfe (1996) and Kollig (1990)
Arrhenius Parameters:
Kb: A= 3.72E+13 [L/(mol*min)]; EA=101200 (J/mol)
Kn: A= 1.37E+13 [L/(mol*min)], EA = 110800 (J/mol)
25 °C Data:
pH 7: Kobs = 5.18E-07; t1/2= 2.54 yr
pH 5.6: Kobs = 5.18E-07; t1/2= 2.54 yr
10 °C Data:
pH 7: Kobs = 4.84E-08; t1/2= 27.2 yr
pH 5.6: Kobs = 4.84E-08; t1/2= 27.2 yr
Dominat hydrolysis products are ethanol and HCl.
The neutral hydrolysis reaction is favored over the alkaline for chloroethane.
Description of key information
Chloroethane hydrolyses in water. The estimated half-life was reported between 38 d and 2.6 years at 25 °C, pH 4, 7 and 9.
Key value for chemical safety assessment
Additional information
Chloroethane (CAS 75-00-3) is not expected to be present in natural waters due to the high vapour pressure of the substance. Thus hydrolysis is not expected to be an important environmental fate process. If present in water, chloroethane is susceptible to slow chemical hydrolysis and forms ethanol and hydrochloric acid as reaction products. The hydrochloric acid formed dissociates at the neutral pH of most natural waters and forms a chloride salt. In water ß-elimination to given olefin and hydrogen halides is rare except at high temperature (ATSDR, 1998).
The hydrolytic half-life of chloroethane is not known with certainty.
Mabey and Mill (1978) reported an estimated hydrolytic half-life in water at 25 °C and pH 7 of 38 days based on a reaction rate constant extrapolated from experimental data at 100 °C.
Jeffers and Wolfe (1996) determined both the neutral and alkaline reaction rates for the hydrolysis of chloroethane. The neutral reaction measured in 0.01 M hydrochloric acid at 25 °C was found to predominate, with a rate constant of 5.1 x 10-7 min-1, resulting in an estimated half-life for chloroethane of 2.6 years.
Chloroethane undergoes neutral and base catalysed hydrolysis to given alcohol. The estimated intercept INB for chloroethane is above pH 11, meaning base catalysed reactions are not important at pH is lower than 11. As no acid catalysed reaction observed, pH conditions in natural waters (pH 4 – 9) are not to have a significant effect on hydrolysis rate constant and half-life for chloroethane (Mabey and Mill, 1978).
Reference
ATSDR (1998). Toxicological profiles for Chloroethane. U.S. Department of Health and human services, Public Health Service, Agency for Toxic Substances and Disease Registry, Division of Toxicology, Atlanta, GA
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