Phthalic acid is an organic compound. It is used in the production of dyes, plastics, and resins. It has carboxylic acid groups and aromatic rings.
| IUPAC Name | Benzene-1,2-dicarboxylic acid |
| Molecular Formula | C8H6O4 |
| CAS Number | 88-99-3 |
| Synonyms | 1,2-Benzenedicarboxylic acid, Orthophthalic acid, O-phthalic acid, PA, 1,2-Phthalic acid |
| InChI | InChI=1S/C8H6O4/c9-7(10)5-3-1-2-4-6(5)8(11)12/h1-4H,(H,9,10)(H,11,12) |
Phthalic Acid Properties
Phthalic Acid Formula
The chemical formula of orthophthalic acid is C8H6O4. It consists of eight carbon atoms, six hydrogen atoms, and four oxygen atoms. The formula represents the composition of orthophthalic acid on a molecular level.
Phthalic Acid Molar Mass
The molar mass of orthophthalic acid is calculated by adding up the atomic masses of its constituent elements. Orthophthalic acid has a molar mass of approximately 166.13 grams per mole. It is derived from the sum of the atomic masses of carbon, hydrogen, and oxygen atoms in the compound.
Phthalic Acid Boiling Point
Orthophthalic acid has a boiling point of approximately 295 degrees Celsius (563 degrees Fahrenheit). This temperature represents the point at which the liquid form of orthophthalic acid changes into a gaseous state under standard atmospheric pressure.
Phthalic Acid Melting Point
The melting point of orthophthalic acid is around 230 degrees Celsius (446 degrees Fahrenheit). It indicates the temperature at which the solid form of orthophthalic acid transforms into a liquid state.
Phthalic Acid Density g/mL
The density of orthophthalic acid is typically around 1.59 grams per milliliter. Density represents the mass of a substance per unit volume, and it provides information about the compactness of the material.
Phthalic Acid Molecular Weight
The molecular weight of orthophthalic acid is approximately 166.13 grams per mole. It signifies the sum of the atomic weights of all atoms present in one molecule of the compound.
Phthalic Acid Structure
Orthophthalic acid has a molecular structure that consists of a benzene ring with two carboxylic acid groups attached to adjacent carbon atoms. This structure gives it its characteristic properties and reactivity in various chemical reactions.
Phthalic Acid Solubility
Orthophthalic acid exhibits moderate solubility in water. It dissolves more readily in organic solvents such as ethanol, methanol, and acetone. The solubility of orthophthalic acid is influenced by factors like temperature, pH, and the nature of the solvent used.
| Appearance | White crystalline powder |
| Specific Gravity | 1.593 g/cm³ |
| Color | Colorless |
| Odor | Odorless |
| Molar Mass | 166.13 g/mol |
| Density | 1.59 g/mL |
| Melting Point | 230 °C |
| Boiling Point | 295 °C |
| Flash Point | 156 °C |
| Water Solubility | 1.7 g/L |
| Solubility | Soluble in organic solvents such as ethanol, methanol, and acetone |
| Vapor Pressure | 0.01 mmHg at 25 °C |
| Vapor Density | 5.75 (air = 1) |
| pKa | 2.89 |
| pH | 2.0 – 3.0 |
Phthalic Acid Safety and Hazards
Orthophthalic acid poses certain safety hazards that need to be considered. It may cause skin and eye irritation upon direct contact. Inhalation of its dust or vapors can irritate the respiratory system. Protective measures, such as gloves and goggles, should be worn when handling this compound. It is also important to work in a well-ventilated area to minimize exposure. Ingestion of orthophthalic acid can be harmful and should be avoided. Additionally, it is advisable to store and handle orthophthalic acid in accordance with proper safety protocols and regulations to prevent accidents or unintended exposure.
| Hazard Symbols | Xn (Harmful) |
| Safety Description | Avoid contact with skin/eyes |
| UN IDs | UN 3077 |
| HS Code | 2917.36.0000 |
| Hazard Class | 9 (Miscellaneous dangerous substances and articles) |
| Packing Group | III (Low danger) |
| Toxicity | Moderately toxic |
Phthalic Acid Synthesis Methods
Various methods can synthesize orthophthalic acid.
One commonly used method involves the oxidation of naphthalene, a hydrocarbon derived from coal tar or petroleum. In this process, naphthalene undergoes controlled oxidation using air or oxygen in the presence of a catalyst, such as vanadium pentoxide or cobalt acetate. Hydrolysis converts the resulting product into orthophthalic acid.
The oxidation of ortho-xylene, a derivative of xylene obtained from petroleum, enables the synthesis of phthalic anhydride. This process involves oxidizing ortho-xylene with air or oxygen in the presence of a catalyst, typically a mixed metal oxide. Subsequently, hydrolysis of phthalic anhydride forms orthophthalic acid.
To synthesize orthophthalic acid, one can employ the carbonylation of phthalic anhydride, using carbon monoxide gas and a catalyst such as rhodium or iridium. This reaction results in the formation of orthophthalic acid.
Overall, these synthesis methods enable the production of orthophthalic acid on a large scale. However, it’s important to note that the specific reaction conditions, catalysts, and purification processes may vary depending on the desired purity and application of the orthophthalic acid being produced.
Phthalic Acid Uses
Orthophthalic acid finds application in various industries due to its versatile properties. Here are some of its common uses:
- Dye Production: The production of dyes, particularly phthalein dyes, utilizes orthophthalic acid as a precursor. Industries such as textiles, printing, and paint use these dyes.
- Plasticizers: Orthophthalic acid plays a key role in producing plasticizers, specifically phthalate esters. Manufacturers add plasticizers to plastics to enhance flexibility, durability, and workability. PVC products like cables, flooring, and coatings widely incorporate plasticizers.
- Resin Manufacturing: Orthophthalic acid acts as a building block for manufacturing alkyd resins, extensively used in coatings, varnishes, and adhesives. These resins offer excellent durability, gloss, and chemical resistance.
- Pharmaceutical Synthesis: Orthophthalic acid serves as an intermediate in synthesizing various pharmaceutical compounds. It acts as a starting material for producing drugs, including antihistamines and diuretics.
- Laboratory Reagent: Researchers employ orthophthalic acid as a reagent in laboratory experiments, particularly in organic synthesis. It enables the introduction of carboxylic acid groups into organic compounds.
- Chemical Intermediates: Orthophthalic acid derivatives function as intermediates in synthesizing other chemicals. These derivatives undergo further reactions to generate compounds like phthalimide, phthalonitrile, and phthaloyl chloride.
- Corrosion Inhibitors: Orthophthalic acid-based compounds serve as corrosion inhibitors across different applications. They aid in protecting metal surfaces from corrosion and degradation in industrial processes.
The diverse range of applications highlights the importance of orthophthalic acid across multiple industries, demonstrating its significance as a versatile chemical compound.
Questions:
Q: How many ml of boiling water are required to dissolve 25g phthalic acid?
A: The exact volume depends on the solubility, but approximately 150 ml of boiling water is needed to dissolve 25g of orthophthalic acid.
Q: What does phthalic acid smell like?
A: Orthophthalic acid is odorless.
Q: What is the boiling point of phthalic acid?
A: The boiling point of orthophthalic acid is approximately 295 °C.
Q: How many grams of phthalic acid would recrystallize out?
A: The amount of orthophthalic acid that recrystallizes depends on factors like cooling rate and impurities present, so it varies.
Q: What is phthalic acid used for?
A: Orthophthalic acid is used in the production of dyes, plastics, resins, pharmaceuticals, and as a laboratory reagent.
Q: How to determine how much water is needed to dissolve phthalic acid?
A: The water needed for dissolution depends on the solubility of orthophthalic acid, which can be determined from experimental data or literature references.
Q: What are the “functional groups” in phthalic acid?
A: The functional groups in orthophthalic acid are two carboxylic acid (-COOH) groups attached to an aromatic ring.
Q: Is phthalic acid soluble?
A: Yes, orthophthalic acid is moderately soluble in water and more soluble in organic solvents.
Q: What would be the effect if phthalic acid was used instead of KHP as the primary stadard for NaOH?
A: The use of orthophthalic acid as a primary standard for NaOH would introduce errors in the determination of NaOH concentration due to differences in molecular weight and stoichiometry.
Q: What mass of dipotassium phthalate must be added to phthalic acid to give a buffer of…?
A: The specific mass of dipotassium phthalate required to create a buffer depends on the desired pH and the concentration of orthophthalic acid.