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para-Anisidine (p-anisidine), a grey-brown solid, is the most toxic[5] of the three isomers of anisidine and causes blood damage upon oral ingestion, inhalation or skin contact. If heated strongly, it may release very toxic fumes of nitrogen oxides.

Skeletal formula of p-anisidine
Ball-and-stick model of p-anisidine
Preferred IUPAC name
Other names
p-Anisidine (no longer recommended[1])
3D model (JSmol)
ECHA InfoCard 100.002.959
EC Number 203-254-2
UN number 2431
Molar mass 123.15 g/mol
Density 1.071 (57 °C)
Melting point 56 to 59 °C (133 to 138 °F; 329 to 332 K)
Boiling point 243 °C (469 °F; 516 K)
Solubility soluble in ethanol, diethyl ether, acetone, benzene
Vapor pressure 0.006 mmHg (25 °C)[2]
-80.56·10−6 cm3/mol
Flash point 122 °C (252 °F; 395 K)
515 °C (959 °F; 788 K)
Lethal dose or concentration (LD, LC):
2900 mg/kg (rabbit, oral)
1300 mg/kg (mouse, oral)
1400 mg/kg (rat, oral)[4]
1000 mg/kg (mouse, oral)[4]
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 0.5 mg/m3 [skin][2]
REL (Recommended)
TWA 0.5 mg/m3 [skin][2]
IDLH (Immediate danger)
50 mg/m3[2]
Related compounds
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

p-Anisidine reacts with secondary oxidation products such as aldehydes and ketones in fats and oils to form products that absorb at 350 nm wavelength of light; therefore, it is used as an official method for detecting them by the American Oil Chemists' Society.[6] It is particularly good at detecting unsaturated aldehydes, which are the ones that are most likely to generate unacceptable flavors, making it particularly useful in food quality testing.[7]


  1. ^ Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 669. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4. The names ‘toluidine’, ‘anisidine’, and ‘phenetidine’ for which o-, m-, and p- have been used to distinguish isomers, and ‘xylidine’ for which numerical locants, such as 2,3-, have been used, are no longer recommended, nor are the corresponding prefixes ‘toluidine’, ‘anisidino’, ‘phenetidine’, and ‘xylidino’. 
  2. ^ a b c d "NIOSH Pocket Guide to Chemical Hazards #0035". National Institute for Occupational Safety and Health (NIOSH). 
  3. ^ Weast, Robert C., ed. (1981). CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, FL: CRC Press. p. C-98. ISBN 0-8493-0462-8. .
  4. ^ a b "p-Anisidine". Immediately Dangerous to Life and Health. National Institute for Occupational Safety and Health (NIOSH). 
  5. ^
  6. ^ "AOCS Official Method Cd 18-90". American Oil Chemists' Society. Retrieved 26 February 2013. 
  7. ^ Steele, Robert (2004). Understanding and Measuring the Shelf-Life of Food. Woodhead Publishing in Food Science and Technology Series. Woodhead Publishing. p. 136. ISBN 1855737329. 

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