Crotoxyphos (Ref: ENT 24717)

Crotoxyphos (Ref: ENT 24717)	Last updated: 25/11/2025
(Also known as: crotoxyfos; cyodrin; decrotox; Kemdrin; ciodrin; SC 4294)

GENERAL INFORMATION

Description

An obsolete organophosphate insecticide used in veterinary medicine for the control of ectoparasites

Examples of veterinary uses

Used to control external insect pests such as flies, mites and ticks

Examples of species treated

Cattle; Pigs; Goats; Horses; Sheep

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Crotoxyphos exhibits both geometric and stereoisomerism. The molecule contains a double bond in the crotonate (but-2-enoate) portion, which gives rise to E/Z (trans/cis) geometric isomers depending on the spatial arrangement of substituents around the double bond. Additionally, crotoxyphos is chiral, due to the presence of a stereogenic centre at the 1-phenylethyl group, meaning it can exist as enantiomers. As a result, the technical material is typically a mixture of isomers, including both geometric and optical forms.

Chemical formula

C₁₄H₁₉O₆P

Canonical SMILES

CC(C1=CC=CC=C1)OC(=O)C=C(C)OP(=O)(OC)OC

Isomeric SMILES

CC(C1=CC=CC=C1)OC(=O)/C=C(\C)/OP(=O)(OC)OC

International Chemical Identifier key (InChIKey)

XXXSILNSXNPGKG-ZHACJKMWSA-N

International Chemical Identifier (InChI)

InChI=1S/C14H19O6P/c1-11(20-21(16,17-3)18-4)10-14(15)19-12(2)13-8-6-5-7-9-13/h5-10,12H,1-4H3/b11-10+

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Antiparasitic

Substance groups

Organophosphate substance

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

A contact and stomach poison. Acetylcholinesterase (AchE) inhibitor.

Molecular targets

[Cholinesterase, Inhibitor]

CAS RN

7700-17-6

EC number

231-720-5

CIPAC number

329

US EPA chemical code

058801

PubChem CID

5371578

Therapeutic Class

ATCvet Code

None allocated

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

314.27

PIN (Preferred Identification Name)

rac-(1R)-1-phenylethyl (2E)-3-[(dimethoxyphosphoryl)oxy]but-2-enoate

IUPAC name

(RS)-1-phenylethyl 3-(dimethoxyphosphinoyloxy)isocrotonate

CAS name

1-phenylethyl (2E)-3-[(dimethoxyphosphinyl)oxy]-2-butenoate

Global Governance status: Listed (✓) under

UK Poisons List Order 1972	Rotterdam Convention	Montreal Protocol
XNo The Poisons List Order 1972	XNo Rotterdam Convention	XNo Montreal Protocol
Stockholm Convention	OSPAR	EU Water Framework Directive
XNo Stockholm Convention	XNo OSPAR	XNo EU Water Framework Directive

Relevant Environmental Water Quality Standards

Forever chemical

Other status information

Physical state

Colourless to light straw-coloured liquid depending upon purity

Commercial

Property

Value

Availability status

Considered obsolete but may be available in some countries

Introduction & key dates

1962, first reported

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

Crown Chemicals
Shell Chemical Co.

Example products using this active

Decrotox
Pantozol
Ciodrin
Duravos

Formulation and application details

Usually supplied as an emulsifiable concentrate

Commercial production

The production of crotoxyphos involves the esterification of crotonic acid with a dimethoxyphosphinylated phenylethanol derivative. The process begins by synthesising the phosphorate moiety, typically dimethyl phosphorochloridate, which is then reacted with 1-phenylethanol under basic conditions to form the intermediate dimethoxyphosphinyl phenylethyl alcohol. This intermediate is subsequently esterified with crotonic acid (specifically the trans-isomer, 2E) using a dehydrating agent such as dicyclohexylcarbodiimide or via acid catalysis to yield crotoxyphos.

Impact on climate of production and use

Published GHG data is not available for most pharmaceuticals. However, according to industry, global averages suggest producing 1 kg of a typical active pharmaceutical ingredient can range from 10 to 100 kg CO₂e for small molecule drugs and potentially up to 1000 kg CO₂e for complex biologicals such as vaccines, depending on the drug type, its formulation, complexity of synthesis, solvent recovery, and energy sources used.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

Solubility - In water at 20 °C at pH 7 (mg l⁻¹)

1000

at 25 °C

Moderate

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

Melting point (°C)

Boiling point (°C)

Degradation point (°C)

Flashpoint (°C)

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

2.00 X 10⁰³

Calculated

Log P

3.3

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

1.9

Low volatility. 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)

1.5

Non-persistent

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

Literature DT₅₀ range 2 to 71 hours (R4)

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Note

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

Value

Note

pH sensitive: 540hrs at pH 2, 410hrs at pH 6 and 180hr at pH 9.0

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)

Moderately mobile

K_oc (mL g⁻¹)

170

Notes and range

Log10 K_oc 2.23

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

0.31

Calculated

Low leachability

Bio-concentration factor

BCF (l kg⁻¹)

CT₅₀ (days)

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

Rat

High

Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Birds - Acute LD₅₀ (mg kg⁻¹)

520

Coturnix japonica

Moderate

Birds - Short term dietary LC₅₀ (mg kg⁻¹ bw d⁻¹)

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

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

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

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)

> 2.31

Moderate

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)

Beneficial insects (Butterflies)

Contact

Notes

Oral

Notes

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

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

0.06

Oncorhynchus mykiss

High

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)

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)

Rat

High

Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)

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

447

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Rat

Other Mammal toxicity endpoints

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

List I

Exposure Routes

Public

Occupational

Mammalian dose elimination route and rate

Rapidly eliminated (~48 hrs) mainly via the urine (~80%)

Health issues

Specific human health issues (hazard-based)

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

Toxic
May cause bradycardia or tachycardia
May cause respiratory problems

Handling issues

Property

Value and interpretation

General

No information available

CLP classification 2013

WHO Classification

Not classified: Obsolete (Not classified: Obsolete)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

crotoxyphos

French

crotoxyphos

German

Crotoxyphos

Danish

Italian

Spanish

crotoxifos

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	25/11/2025
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

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