493-52-7 Usage
Description
Methyl Red is an azo dye that serves as an acid-base indicator, commonly used in various scientific applications. It is a dark red crystalline powder and is structurally similar to methyl orange. Methyl Red changes color depending on the pH of the solution it is in, turning red when the pH is below 4.4 and yellow when the pH is above 6.2.
Uses
1. Used as a pH indicator for acid-base titrations:
Methyl Red is used as an indicator in 0.1% alcoholic solution, with a pH range of 4.4 (red) to 6.2 (yellow). It is particularly useful for titrating ammonia (NH3) and weak organic bases, such as alkaloids. However, it is not suitable for titrating organic acids, except for oxalic and picric acid. Methyl Red is easily reduced, causing it to lose its color, so readings should be made promptly. It is gradually being replaced by more stable sulfonphthalein indicators, such as bromcresol green, which exhibit a sharper change in color.
2. Used in microbiology for bacterial identification:
In microbiology, Methyl Red is used to identify bacteria that produce stable acids through mixed acid fermentation of glucose. The test involves adding Methyl Red to an overnight culture grown in MRVP broth. If the organism uses the mixed acid fermentation pathway and produces stable acidic end-products, the Methyl Red will stay red, indicating the presence of acidic end products.
3. Used in the study of degradation using Fenton's reagent:
Methyl Red is also used as a pH indicator in the pH range of 4.2 6.3 to study its degradation using Fenton's reagent.
4. General Description and Properties:
Methyl Red solution is an azo dye that turns red when the pH is below 4.4. It is moderately soluble in ethanol and insoluble in water. When alcohol solution is added to hydrochloric acid, it turns purple, and when sodium hydroxide is added, it turns dim yellow. This property is utilized to differentiate enteric bacteria based on their metabolic pathways and the resulting pH changes in the medium.
5. Chemical Properties:
Methyl Red is an organic dye with a dark red crystalline powder form. It consists of benzoic acid substituted at position 2 by a 4-[(dimethylamino)phenyl]diazenyl group. It is an acid-base indicator that is red in solutions below a pH of 4.2 and yellow above a pH of 6.3. The transition range of Methyl Red is nearer neutral (pH 7) than that of methyl orange, making it suitable for a variety of titrations and scientific applications.
Preparation
2-Aminobenzoic acid?diazo, and N,N-dimethylaniline coupling.
Hazard
Questionable carcinogen.
Biochem/physiol Actions
Methyl Red is a maroon red crystal azo dye. Methyl Red is a pH indicator and changes color at a pH of 5.5. Methyl Red is widely used in saliva sampling method. In addition, it is also employed in carbohydrate and lactic acid detection. Methyl Red has been effectively used for intrageneric differentiation of Enterobacteriaceae.
Safety Profile
Questionable
carcinogen with experimental tumorigenic
data. Mutation data reported. When heated
to decomposition it emits toxic fumes of
NOx.
Purification Methods
The acid is extracted with boiling toluene using a Soxhlet apparatus. The crystals which separate on slow cooling to room temperature are filtered off, washed with a little toluene and recrystallised from glacial acetic acid, *benzene or toluene followed by pyridine/water. Alternatively, dissolve it in aqueous 5% NaHCO3 solution, and precipitate it from a hot solution by dropwise addition of aqueous HCl. Repeat this until the extinction coefficients do not increase. [Beilstein 16 IV 504.]
Check Digit Verification of cas no
The CAS Registry Mumber 493-52-7 includes 6 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 3 digits, 4,9 and 3 respectively; the second part has 2 digits, 5 and 2 respectively.
Calculate Digit Verification of CAS Registry Number 493-52:
(5*4)+(4*9)+(3*3)+(2*5)+(1*2)=77
77 % 10 = 7
So 493-52-7 is a valid CAS Registry Number.
InChI:InChI=1/C15H15N3O2/c1-18(2)12-8-9-14(13(10-12)15(19)20)17-16-11-6-4-3-5-7-11/h3-10H,1-2H3,(H,19,20)/b17-16+
493-52-7Relevant articles and documents
Interaction of Platinum(II) Complexes with Methyl Red
Gel'fman,Kirsanova
, p. 1090 - 1093 (2008/10/08)
The interaction of K2[PtCl4], K2[PtI4], [PtThio4]Cl2, cis- and trans-[Pt(NH3)2Cl2], and [Pt(NH3)4]Cl2 with Methyl Red (HL) was studied. It was found that HL forms stable complexes, where it may be a mono- or bidentate ligand. The thermodinamical stability of trans-[Pt(NH3)2(LH)Cl]NO3 was studied potentiometrically. The results obtained show that the azo group possesses π acceptor abilities.
