Chloral hydrate

Chloral hydrate	Last updated: 11/09/2025
(Also known as: aquachloral; chorhydrate)

SUMMARY

Chloral hydrate is an obsolete herbicide. It is a highly volatile substance which is not highly toxic to aquatic species. Chloral hydrate is moderately toxic to mammals if ingested. It is also carcinogenic and an irritant.

GENERAL INFORMATION

Description

A chemical substance sometimes used in veterinary medicine as a hypnotic and sedative but now largely obsolete

Examples of veterinary uses

Used as a general anesthetic

Examples of species treated

Cattle; Horses

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

None

Chemical formula

C₂H₃Cl₃O₂

Canonical SMILES

C(C(Cl)(Cl)Cl)(O)O

Isomeric SMILES

International Chemical Identifier key (InChIKey)

RNFNDJAIBTYOQL-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C2H3Cl3O2/c3-2(4,5)1(6)7/h1,6-7H

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
chloral hydrate	-

General status

Veterinary substance type

General anesthetic

Substance groups

Organochloride herbicide

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Molecular targets

[GABA_A receptor, Positive allosteric modulator]

CAS RN

302-17-0

EC number

206-117-5

CIPAC number

None allocated

US EPA chemical code

268100

PubChem CID

2707

CLP index number

605-014-00-6

Therapeutic Class

Hypnotics & sedatives: Aldehydes and derivatives

ATCvet Code

QN05CC

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

165.42

PIN (Preferred Identification Name)

2,2,2-trichloroethane-1,1-diol

IUPAC name

2,2,2-trichloroethane-1,1-diol

CAS name

2,2,2-tricloro-1,1-ethandiol

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

Colourless crystals, hygroscopicith characteristic odour

Commercial

Property

Value

Availability status

Considered obsolete but may be available in some countries

Introduction & key dates

1832, first discovered Germany

Example manufacturers & suppliers of products using this active now or historically

Chemiekombinat Bitterfield
Active Pharma Supplies Ltd

Example products using this active

Bi 3411
Aquachloral
Noctec

Formulation and application details

Usually formulated for crop use as foliar sprays, soil drenches and seed treatments. For animal use it is primarily formulated as a sterile injectable solution, typically administered intravenously (IV)

Commercial production

The commercial production of chloral hydrate involves a chemical synthesis process starting with ethanol or acetaldehyde as the primary feedstock. The most common method is the chlorination of ethanol in the presence of hydrochloric acid, which produces chloral. This intermediate is then reacted with water to form chloral hydrate

Impact on climate of production and use

Data for the amount of life cycle GHGs produced by chloral hydrate are not available in the public domain. However, whilst estimates vary, more general data suggests that between 18 and 27 kilograms of CO₂e is emitted per kilogram of herbicide produced.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

Solubility - In water at 20 °C (mg l⁻¹)

3830000

High

Solubility - In organic solvents at 20 °C (mg l⁻¹)

Melting point (°C)

51.6

Boiling point (°C)

98.0

Degradation point (°C)

97.0

Flashpoint (°C)

Octanol-water partition coefficient at pH 7, 20 °C

9.77 X 10⁰⁰

Calculated

Log P

0.99

Low

Fat solubility of residues

Solubility

Likely to be soluble

Data type

Based on chemical group

Density (g ml⁻¹)

1.91

Dissociation constant pKa) at 25 °C

6.8

Vapour pressure at 20 °C (mPa)

4.7 X 10⁰⁶

Highly volatile. If applied directly to plants or soil, drift is a concern & mitigation is advisable

Henry's law constant at 25 °C (Pa m³ mol⁻¹)

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

Maximum UV-vis absorption L mol⁻¹ cm⁻¹

Surface tension (mN m⁻¹)

Refractive Index

Environmental release

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Note

Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7

Value

Note

Water-sediment DT₅₀ (days)

Water phase only DT₅₀ (days)

Sediment phase only DT₅₀ (days)

Air degradation

As this parameter is not normally measured directly, a surrogate measure is used: ‘Photochemical oxidative DT₅₀’. Where data is available, this can be found in the Fate Indices section below.

Decay in stored produce DT₅₀

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

K_oc (mL g⁻¹)

Notes and range

Freundlich

K_f (mL g⁻¹)

K_foc (mL g⁻¹)

¹/_n

Notes and range

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

Bio-concentration factor

BCF (l kg⁻¹)

CT₅₀ (days)

Known soil metabolites

Metabolite

Major/Minor fraction

$Click here for further information on Major/Minor fraction$

Estimated maximum occurrence fraction

Notes

TCA

Major fraction

Known groundwater metabolites

None

Other known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

1080

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

(ppm diet)

Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)

Birds - Acute LD₅₀ (mg kg⁻¹)

Birds - Short term dietary (LC₅₀/LD₅₀)

Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)

Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)

Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)

Soil micro-organisms

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Non-target plants

Vegetative vigour ER₅₀ (g ha⁻¹)

Seedling emergence ER₅₀ (g ha⁻¹)

Honeybees (Apis spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Chronic

Notes

Bumblebees (Bombus spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Mason bees (Osmia spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Other bee species (1)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

Other bee species (2)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

Beneficial insects (Ladybirds)

Beneficial insects (Lacewings)

Beneficial insects (Parasitic wasps)

Beneficial insects (Predatory mites)

Beneficial insects (Ground beetles)

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Temperate Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

200

Perca fluviatilis

Low

Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)

Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

Temperate Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

> 245

Daphnia magna

Low

Temperate Freshwater Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)

Tropical Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)

Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)

Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)

Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)

Aquatic Plants (free-floating, fonds growth, fresh) - 7 day (mg l⁻¹)

Aquatic plants (rooted, growth rate, fresh) - 14 day (mg l⁻¹)

Algae - Acute (growth rate, fresh; mg l⁻¹)

Algae - Chronic (growth rate, fresh; mg l⁻¹)

Mesocosm study data

NOEAEC mg l⁻¹

Marine bivalves

HUMAN HEALTH AND PROTECTION

General

Property

Value

Source; quality score; and other information

Interpretation

Threshold of Toxicological Concern (Cramer Class)

High (class III)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

1080

Rat

Moderate

Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)

3030

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

Intraperitoneal LD₅₀ = 472 mg kg⁻¹

Rat

ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)

ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)

AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)

AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

Exposure Routes

Public

Occupational

Mammalian dose elimination route and rate

Hetaptic metabolism. Excreted in the bile, faeces & urine

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

No data found

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

May induce sedative & hypnotic effects
CNS & heart toxicant
May cause diarrhoea, dizziness and nausea
Possible liver & kidney toxicant

Handling issues

Property

Value and interpretation

General

Slightly corrosive to metals
Incompatible with strong bases and oxidisers

CLP classification 2013

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

chloral hydrate

French

hydrate de chloral

German

Chloraldurat

Danish

Italian

Spanish

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	11/09/2025
Contact:	aeru@herts.ac.uk
Please cite as:	Lewis, K.A., Tzilivakis, J., Warner, D. and Green, A. (2016) An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal, 22(4), 1050-1064. DOI: 10.1080/10807039.2015.1133242