Alizarin (1,2-dihydroxyanthraquinone) is a red dye derived from anthraquinone. It is synthesized by treating anthracene with potassium hydroxide and sulfuric acid. Alizarin is used in textile, paper, and cosmetics industries.
| IUPAC Name | 1,2-dihydroxyanthracene-9,10-dione |
| Molecular Formula | C14H8O4 |
| CAS Number | 72-48-0 |
| Synonyms | 1,2-Anthraquinone-diol; 1,2-Dihydroxyanthraquinone; 9,10-Anthracenedione, 1,2-dihydroxy-; Alizarine; C.I. 58000; Turkey Red |
| InChI | InChI=1S/C14H8O4/c15-10-6-5-8-9(13(10)17)11(16)7-3-1-2-4-12(7)18/h1-6,15-16H |
Alizarin Molar Mass
Alizarin has a molar mass of 240.22 g/mol. This value is calculated by adding the atomic weights of carbon, hydrogen, and oxygen atoms present in its chemical formula, which is C14H8O4. The molar mass of a compound is an important parameter for various calculations, such as determining the amount of substance required to prepare a solution of known concentration or the number of moles present in a given mass of the compound.
1,2-dihydroxyanthraquinone Boiling Point
The boiling point of 1,2-dihydroxyanthraquinone is 430 °C (806 °F). This temperature is the point at which the vapor pressure of the liquid is equal to the external pressure applied to the liquid. It is important to note that the boiling point of a compound can vary based on factors such as pressure and purity.
1,2-dihydroxyanthraquinone Melting Point
The melting point of 1,2-dihydroxyanthraquinone is 289-290 °C (552-554 °F). This temperature is the point at which the solid form of the compound changes to the liquid form. It is important to note that the melting point of a compound can vary based on factors such as pressure and purity.
1,2-dihydroxyanthraquinone Density g/ml
The density of 1,2-dihydroxyanthraquinone is 1.52 g/mL. Density is a measure of how much mass is contained within a given volume of a substance. This property is useful in various applications, such as determining the buoyancy of a substance and estimating the mass of a given volume of a substance.
1,2-dihydroxyanthraquinone Molecular Weight
The molecular weight of 1,2-dihydroxyanthraquinone is 240.22 g/mol. This value is the sum of the atomic weights of all the atoms present in the molecule. It is an important parameter for various calculations, such as determining the molar concentration of a solution or the number of moles present in a given mass of the compound.
1,2-dihydroxyanthraquinone Structure
1,2-dihydroxyanthraquinone has a planar structure with two hydroxyl groups attached to the anthraquinone ring system. The molecule has a conjugated system of pi bonds that gives it its characteristic red color. The presence of the two hydroxyl groups allows for hydrogen bonding, which contributes to the stability of the solid form of the compound.
1,2-dihydroxyanthraquinone Formula
The chemical formula for 1,2-dihydroxyanthraquinone is C14H8O4. This formula represents the types and numbers of atoms present in the molecule. The molecular formula is important for various calculations, such as determining the molecular weight of the compound and the number of moles present in a given mass of the compound.
| Appearance | Red crystalline powder |
| Specific Gravity | 1.52 |
| Color | Red |
| Odor | Odorless |
| Molar Mass | 240.22 g/mol |
| Density | 1.52 g/mL |
| Melting Point | 289-290 °C (552-554 °F) |
| Boiling Point | 430 °C (806 °F) |
| Flash Point | Not applicable |
| Water Solubility | 0.02 g/L (20 °C) |
| Solubility | Soluble in ethanol, ether, benzene, and chloroform |
| Vapour Pressure | Not applicable |
| Vapour Density | Not applicable |
| pKa | 8.24 |
| pH | 6.3 (0.1% aq. soln.) |
Alizarin Safety and Hazards
Alizarin (1,2-dihydroxyanthraquinone) can pose certain safety hazards if not handled properly. It can cause skin, eye, and respiratory tract irritation upon exposure. Ingestion or inhalation of large amounts of alizarin can lead to vomiting, diarrhea, and kidney damage. It is also a flammable substance and can ignite when exposed to heat or flames. Proper personal protective equipment, including gloves, goggles, and respirators, should be worn when handling alizarin. It should be stored in a cool, dry, and well-ventilated area away from heat sources and incompatible materials. In case of accidental ingestion, inhalation, or skin/eye contact, immediate medical attention should be sought.
| Hazard Symbols | Xn, N |
| Safety Description | Keep away from heat, sparks, and open flames. Avoid breathing dust/fume/gas/mist/vapors/spray. Wear protective gloves/protective clothing/eye protection/face protection. |
| UN IDs | UN 3077 |
| HS Code | 3204.15.90 |
| Hazard Class | 9 |
| Packing Group | III |
| Toxicity | May cause irritation and damage to skin, eyes, and respiratory system. Ingestion or inhalation of large amounts may cause vomiting, diarrhea, and kidney damage. Chronic exposure may cause cancer. |
Alizarin Synthesis Methods
To synthesize alizarin (1,2-dihydroxyanthraquinone), one can use several methods. One of the most commonly employed methods involves oxidizing anthraquinone using a mixture of nitric and chromic acids to produce anthraquinone-2-sulfonic acid. Then, hydrolyzing the sulfonic acid using sulfuric acid results in the formation of 1,2-dihydroxyanthraquinone.
Another method requires reducing anthraquinone by using sodium dithionite in the presence of sodium hydroxide to form anthrahydroquinone. This compound is further oxidized using potassium permanganate to form 1,2-dihydroxyanthraquinone.
To synthesize 1,2-dihydroxyanthraquinone, one can react phthalic anhydride and resorcinol in the presence of a zinc chloride catalyst, resulting in the formation of 1,2-dihydroxyanthraquinone. The next step involves oxidizing 1,2-dihydroxyanthraquinone to 1,2-dihydroxyanthraquinone using chromic acid.
In addition to these traditional methods, researchers have explored modern techniques such as microwave-assisted synthesis, ultrasound-assisted synthesis, and enzymatic synthesis as alternative methods for synthesizing 1,2-dihydroxyanthraquinone.
It is important to note that these synthesis methods may involve the use of hazardous chemicals and conditions, and trained professionals should carry them out in a properly equipped laboratory with the use of personal protective equipment to ensure safety.
Alizarin Uses
Alizarin (1,2-dihydroxyanthraquinone) has several uses in various fields. Some of its uses are:
- 1,2-dihydroxyanthraquinone finds application in the textile industry as a dye for coloring cotton, wool, silk, and leather.
- Traditional Chinese medicine employs 1,2-dihydroxyanthraquinone to treat various diseases such as hemorrhages, jaundice, and menstrual disorders.
- Analytical chemistry uses 1,2-dihydroxyanthraquinone as a pH indicator in a transition range of pH 5.0-6.8.
- 1,2-dihydroxyanthraquinone is a starting material for synthesizing other organic compounds, including anthraquinone and quinizarin.
- Biologists use 1,2-dihydroxyanthraquinone for visualizing bone tissue and calcium deposits in staining techniques.
- Photographers use 1,2-dihydroxyanthraquinone as a photographic developer to produce black and white photographs.
- Manufacturers of ink, paint, and varnish use 1,2-dihydroxyanthraquinone in various industrial applications.
It is important to note that 1,2-dihydroxyanthraquinone can pose certain safety hazards if not handled properly, and proper safety precautions should be taken when working with this compound.
Questions:
Q: What color is alizarin crimson?
A: Alizarin crimson is a deep, red color with a slightly blue undertone. It is commonly used in painting and dyeing.
Q: How to make alizarin crimson?
A: Alizarin crimson can be made by mixing a red pigment, such as cadmium red, with a small amount of a blue pigment, such as ultramarine blue. This mixture can then be modified by adding small amounts of other pigments, such as burnt sienna or yellow ochre, to achieve the desired hue and tone. Alternatively, artists can purchase pre-made tubes of alizarin crimson paint from art supply stores. It is important to note that the chemical compound alizarin (1,2-dihydroxyanthraquinone) is not used in the production of alizarin crimson paint, and is typically only used in industrial or scientific applications.