Propyl Red is a synthetic azo dye and pH indicator known for its reddish-orange color and distinct response to changes in acidity. The chemical formula is 2-[4-(dipropylamino)phenylazo]benzoic acid and contains an N,N-dipropylamino group that affects its physicochemical properties. It has a pKa of approximately 5.48 and changes from red to yellow over a pH range of about 4.8 to 6.6. Its lipophilic character and good solubility in organic solvents make the propyl red suitable for colorimetric measurements in non-aqueous and mixed-phase systems.
CAS No.: 2641-01-2
Synonyms: 2-[4-(Dipropylamino)phenylazo]benzoic acid, 4-(Dipropylamino)azobenzene-2′-carboxylic acid.
| Physical Properties | |
| Chemical formula | C19H23N3O2 |
| IUPAC Name | 2-[[4-(dipropylamino)phenyl]diazenyl]benzoic acid |
| Molecular weight | 325.4Â g/mol |
| Appearance | Reddish crystalline powder |
| Solubility | Insoluble in water |
| Storage | Store at room temperature |
| Chemical Properties | |
| Color | Yellow- Orange |
| Physical State | Solid |
| Melting Point | 173-175° C |
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| Pictograms : |  |
| Hazard Statements : | H413: May cause long-lasting harmful effects to aquatic life |
| Precautionary Statements: | P273: Avoid release to the environment. |
Propyl Red is a synthetic azo dye and pH indicator known for its reddish-orange color and distinct response to changes in acidity. The chemical formula is 2-[4-(dipropylamino)phenylazo]benzoic acid and contains an N,N-dipropylamino group that affects its physicochemical properties. It has a pKa of approximately 5.48 and changes from red to yellow over a pH range of about 4.8 to 6.6. Its lipophilic character and good solubility in organic solvents make the propyl red suitable for colorimetric measurements in non-aqueous and mixed-phase systems.
CAS No.: 2641-01-2
Synonyms: 2-[4-(Dipropylamino)phenylazo]benzoic acid, 4-(Dipropylamino)azobenzene-2′-carboxylic acid.
| Physical Properties | |
| Chemical formula | C19H23N3O2 |
| IUPAC Name | 2-[[4-(dipropylamino)phenyl]diazenyl]benzoic acid |
| Molecular weight | 325.4Â g/mol |
| Appearance | Reddish crystalline powder |
| Solubility | Insoluble in water |
| Storage | Store at room temperature |
| Chemical Properties | |
| Color | Yellow- Orange |
| Physical State | Solid |
| Melting Point | 173-175° C |
Â
| Pictograms : | |
| Hazard Statements : | H413: May cause long-lasting harmful effects to aquatic life |
| Precautionary Statements: | P273: Avoid release to the environment. |
Propyl Red is mainly used for pH measurement, biological staining and analytical research. It is also used in microbiological and industrial coloring applications.
Propyl Red and Methyl Red are both azo dyes used as pH indicators but Propyl Red contains longer propyl groups which make it more hydrophobic and lipophilic than Methyl Red.
