Neopentane is a highly branched hydrocarbon with four methyl groups attached to a central carbon atom. It is commonly used as a reference compound in NMR spectroscopy and as a fuel additive.
| IUPAC Name | 2,2-dimethylpropane |
| Molecular Formula | C5H12 |
| CAS Number | 463-82-1 |
| Synonyms | Dimethylpropane, Tetramethylmethane, 2,2-dimethylpropane, Neo-C5H12, UN 2043 |
| InChI | InChI=1S/C5H12/c1-5(2,3)4/h1-4H3 |
Neopentane Structure
Neopentane has a highly branched structure, with four methyl groups attached to a central carbon atom. The molecule is symmetrical and tetrahedral, with a bond angle of 109.5° between each pair of adjacent carbon atoms. The neopentane molecule is nonpolar, with only weak van der Waals forces between its molecules.
Neopentane Boiling Point
The boiling point of neopentane is -9.5°C (-15°F) at standard pressure. This low boiling point is due to the weak intermolecular forces between its molecules, which makes it relatively easy to vaporize. Neopentane is a colorless gas at room temperature and pressure, and it is commonly used as a reference compound for gas chromatography.
Neopentane Molar Mass
Neopentane, also known as 2,2-dimethylpropane, has a molar mass of 72.15 g/mol. It is a highly branched hydrocarbon with four methyl groups attached to a central carbon atom. The molar mass of neopentane can be calculated by summing the atomic weights of all the atoms in its molecular formula, which is C5H12.
Neopentane Melting Point
The melting point of neopentane is -16.6°C (2°F) at standard pressure. Like its boiling point, the low melting point of neopentane is a result of its weak intermolecular forces. Neopentane is a nonpolar molecule with only weak van der Waals forces between its molecules, so it does not form strong crystal structures.
Neopentane Density g/ml
The density of neopentane is 0.623 g/mL at standard temperature and pressure. This low density is due to the low molecular weight of neopentane, which is only 72.15 g/mol. Neopentane is less dense than water, so it will float on top of water if the two are mixed together.
Neopentane Molecular Weight
The molecular weight of tetramethylmethane is 72.15 g/mol. This value represents the sum of the atomic weights of all the atoms in the molecule, which is composed of five carbon atoms and 12 hydrogen atoms. The small molecular weight of tetramethylmethane makes it a highly volatile and flammable compound.
Tetramethylmethane Formula
The molecular formula of tetramethylmethane is C5H12, which represents the number and types of atoms present in the molecule. The formula indicates that there are five carbon atoms and 12 hydrogen atoms in the tetramethylmethane molecule. The molecular formula does not provide information about the arrangement of atoms within the molecule, which is determined by its structure.
| Appearance | Colorless gas |
| Specific Gravity | 0.623 g/mL at 20°C |
| Color | Colorless |
| Odor | Odorless |
| Molar Mass | 72.15 g/mol |
| Density | 0.623 g/mL at 20°C |
| Melting Point | -16.6°C |
| Boiling Point | -9.5°C |
| Flash Point | -49°C |
| Water Solubility | 0.04 g/L at 20°C |
| Solubility | Insoluble in water |
| Vapor Pressure | 566 mmHg at 20°C |
| Vapor Density | 2.5 (air = 1) |
| pKa | ~50 |
| pH | Not applicable |
Neopentane Safety and Hazards
Tetramethylmethane is a highly flammable gas and can form explosive mixtures with air. It can also cause frostbite if it comes into contact with the skin, as it has a very low boiling point of -9.5°C. Inhaling tetramethylmethane gas can cause dizziness, nausea, and headaches. It is important to handle tetramethylmethane with care and to avoid exposure to flames, sparks, or other sources of ignition. Tetramethylmethane should be stored in a cool, dry, and well-ventilated area, away from heat and oxidizing agents. Proper personal protective equipment, such as gloves and goggles, should be worn when handling tetramethylmethane.
| Hazard Symbols | F+ |
| Safety Description | Highly flammable gas. May cause frostbite. Use only in a well-ventilated area. Keep away from heat and sources of ignition. Wear protective gloves and goggles. |
| UN ID | UN2451 |
| HS Code | 2901.1 |
| Hazard Class | 2.1 |
| Packing Group | None |
| Toxicity | Low toxicity |
Neopentane Synthesis Methods
Several different methods exist for synthesizing tetramethylmethane.
One common method involves the reaction of isobutene and formaldehyde over a solid acid catalyst, such as zeolite. The reaction produces neopentyl alcohol, and one can then dehydrate it to yield tetramethylmethane.
Another method for tetramethylmethane synthesis involves the thermal decomposition of 2,2-dimethylpropane at high temperatures. This reaction yields tetramethylmethane and other hydrocarbons.
A third method involves the reaction of ethyl chloride and zinc in the presence of magnesium to produce diethylzinc, which can then react with isobutylene to produce tetramethylmethane.
One can synthesize tetramethylmethane by hydrogenating isopentene, which results from dehydrogenating isopentane.
Depending on various factors like the availability of raw materials, cost, and desired yield and purity of the final product, different tetramethylmethane synthesis methods can be tailored.
Neopentane Uses
Tetramethylmethane has several important industrial and scientific applications.
- It is used as a reference material for gas chromatography, thanks to its high purity and well-defined properties.
- Tetramethylmethane is also used as a standard for calorimetry and thermodynamics measurements.
- Another major use of tetramethylmethane is as a blowing agent in the production of polyurethane foams, which are used in a wide range of applications, such as insulation, cushioning, and packaging.
- It is used as a refrigerant in cooling systems, due to its low boiling point and good thermodynamic properties. However, its use as a refrigerant has been largely phased out due to its high flammability and potential environmental impacts.
- Tetramethylmethane is also used in the synthesis of other organic compounds, such as neopentyl glycol, which is used in the production of resins, coatings, and plastics.
Its unique properties make it a versatile and valuable compound for various industrial and scientific applications. However, potential hazards of tetramethylmethane must be carefully considered and managed in order to ensure safe and responsible use.
Questions:
Q: How many chiral carbon atoms does neopentane (2,2-dimethylpropane) have?
A: Neopentane does not have any chiral carbon atoms. It is a symmetric molecule with a tetrahedral geometry around each carbon atom, so all carbon atoms are equivalent.
Q: Which has the highest boiling point: hexane, pentane, or neopentane?
A: Hexane has the highest boiling point, followed by pentane and then neopentane. This is because the boiling point of a hydrocarbon increases with its molecular weight and surface area, as well as the strength of its intermolecular forces. Hexane has the highest molecular weight and surface area among the three compounds and also has the strongest intermolecular forces due to its linear structure, leading to a higher boiling point. Pentane and neopentane have lower boiling points due to their smaller molecular size and weaker intermolecular forces.