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Physical & Chemical properties

Melting point / freezing point

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Reference
Endpoint:
melting point/freezing point
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Reason / purpose:
reference to same study
Principles of method if other than guideline:
Classical method
Type of method:
other: not specified
Key result
Melting / freezing pt.:
> 71.5 - < 71.7 °C
Conclusions:
The melting point of the test item is 71.5 - 71.7°C.

Description of key information

The melting point of crotonic acid, pure trans isomer, is about 72 °C.
The melting point of commercial crotonic acid is in the range of 69 - 72 °C

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
72 °C

Additional information

The melting point of Crotonic acid has been reported in a multitude of publications (e.g. www.reaxys.com; Beilsteins Handbuch der Organischen Chemie, etc.).

 

Typical statements, related to the trans-isomer [CASRN 107-93-7] range from 69°C to 73°C.

Typical statements, related to the unspecific CASRN 3724-65-0 range from 70°C to 73°C.

The melting/freezing point of isocrotonic acid [CASRN 503-64-0] has been reported in the range of about 12.5°C to 16°C.

 

This leads to the conclusion that the melting point of Crotonic acid, with a very high purity in regard to the trans-isomer, is about 72°C.

 

Crotonic acid containing a relevant portion of the cis-isomer (isocrotonic acid) should show a significant melting point depression.

 

Commercially available Crotonic acid, whether related to the CASRN 107-93-7 or to the CASRN 3724-65-0, shows melting points within the narrow range of 69 – 73°C.

This finding clearly indicates that, independent of the CASRN assigned, commercial Crotonic acid is always the same substance, containing only minor quantities, if at all, of the cis-isomer.

 

Isocrotonic acid [CASRN 503-64-0] is not commercially available.

 

For these reasons the CASRN 107-93-7 and the related EINECS no. 223-077-4 has been chosen as the key identifiers within this dossier covering all commercial available qualities of Crotonic acid.