The difference between propylene glycol and n-propanol

In the chemical industry, it is essential to understand the properties of substances and their differences. Propylene glycol (chemical formula: HOCH₂ CH₂ OH) and n-propanol (chemical formula: CHy3 CH₂ CH₂ OH) are two easily confused alcohols. Although they are similar in chemical structure, there are significant differences in certain key aspects. This article will analyze the difference between propylene glycol and n-propanol in depth, covering the molecular structure, use and identification methods, to help readers fully understand the characteristics of the two.

---

1. molecular structure and similarities and differences

1. molecular structure
   propylene glycol and n-propanol are both alcohols containing two hydroxyl groups (-OH), but their molecular structures are significantly different.

• Propylene Glycol: The molecular structure is ethylene glycol (-CH₂ CH₂-) with two hydroxyl groups directly connected, and the molecular formula is C₂ H₂ OH.
• n-propanol: The molecular structure is a methyl group (-CH,-CH-,-CH-) linked propanol with a molecular formula of C? H? OH.

1. Structural Similarities and Differences Analysis

• number of carbon atoms propylene glycol contains two carbon atoms, while n-propanol contains three carbon atoms.
• hydroxyl position: The two hydroxyl groups of propylene glycol are located on the same carbon chain, while the hydroxyl group of n-propanol is located on one of the terminal carbon atoms of the longest carbon chain.
• Symmetry propylene glycol has a high symmetry, while n-propanol does not have symmetry.

From the above analysis, it can be seen that there are significant differences in the molecular structure of propylene glycol and n-propanol, which directly affects their physical and chemical properties.

---

2. uses and application areas

1. use of Propylene Glycol Propylene glycol is mainly used as a component in biofuels, such as biodiesel and biodiesel alternative fuels. It is also widely used in the food industry, cosmetics and pharmaceuticals. For example, propylene glycol can be used as a solvent, surfactant, or catalyst to participate in various reaction processes.

2. Use of n-propanol N-propanol is mainly used as chemical raw materials, especially oxygen and intermediate products in the chlor-alkali industry. For example, n-propanol can be used in the manufacture of plastics such as polypropylene, as well as in the pharmaceutical industry as a solvent or fragrance base.

3. Summary of differences in use

• the use of propylene glycol is more inclined to bio-based and food fields, while n-propanol is mainly used as chemical raw materials.
• The molecular structure of n-propanol gives it unique advantages in some industrial applications, while propylene glycol has more advantages in biological applications due to its structural symmetry.

---

3. Identification Methods and Skills

1. physical Property Test

• density: The density of propylene glycol is about 0.971g/cm³, while the density of n-propanol is about 0.800g/cm³. The two can be distinguished by measuring the density of the liquid.
• refractive index propylene glycol has a refractive index of 1.335, while n-propanol has a refractive index of 1.333. Identification can also be assisted by measuring the refractive index.

1. CHEMICAL PROPERTY TESTING

• acidification propylene glycol is easy to decompose under acidic conditions, while n-propanol is more stable.
• oxidation reaction: Propylene glycol can be oxidized in oxygen, while the oxidation reaction of n-propanol is faster.
• Reaction with alkali when propylene glycol reacts with alkali, it will generate flammable gas, and the reaction product of n-propanol is more stable.

1. instrumental analysis

• infrared Spectroscopy (IR): The infrared spectra of propylene glycol and n-propanol have different absorption peaks in the hydroxyl-O-H region, and the two can be distinguished by this.
• Nuclear Magnetic Resonance (NMR) the symmetry of the molecular structure of propylene glycol makes its nuclear magnetic resonance spectrum characteristics obvious, while n-propanol has a number of different chemical environment hydrogen atoms, the spectral line is more complex.

Through the above identification method, it can accurately determine whether the substance to be tested is propylene glycol or n-propanol.

---

4. summary and recommendations

1. main differences

• molecular structure: Propylene glycol is a glycol, and n-propanol is a trihydric alcohol.
• Field of use propylene glycol is mainly used in bio-based and food industries, while n-propanol is used as a chemical raw material.
• Physical Properties the density and refractive index of propylene glycol are higher than that of n-propanol.

1. Select Recommendations
   in practical applications, the choice of propylene glycol or n-propanol needs to be weighed according to specific industrial needs and processing techniques. Propylene glycol is more suitable as a bio-based material due to its biological characteristics, while n-propanol has more advantages in chemical production.

Through the detailed analysis of this article, we hope that readers can clearly understand the difference between propylene glycol and n-propanol, and make the right choice in practical work.