Neopentane

Neopentane

Names
Preferred IUPAC name 2,2-Dimethylpropane
Other names neopentane (no longer recommended) tetramethylmethane
Identifiers
CAS Number	463-82-1 Y
3D model (Jmol)	Interactive image
Beilstein Reference	1730722
ChEBI	CHEBI:30358 Y
ChemSpider	9646 Y
ECHA InfoCard	100.006.677
EC Number	207-343-7
Gmelin Reference	1850
MeSH	neopentane
PubChem	10041
UNII	M863R1J0BP N
InChI InChI=1S/C5H12/c1-5(2,3)4/h1-4H3 Y Key: CRSOQBOWXPBRES-UHFFFAOYSA-N Y
SMILES CC(C)(C)C
Properties
Chemical formula	C5H12
Molar mass	72.15 g·mol−1
Appearance	Colorless gas
Odor	Odorless
Density	586 mg mL−1
Melting point	−21 to −15 °C; −6 to 5 °F; 252 to 258 K
Boiling point	9.0 to 10.0 °C; 48.1 to 49.9 °F; 282.1 to 283.1 K
Vapor pressure	146 kPa (at 20 °C)
Henry's law constant (kH)	4.7 nmol Pa−1 kg−1
Thermochemistry
Specific heat capacity (C)	121.07–120.57 J K−1 mol−1
Std molar entropy (So298)	217 J K−1 mol−1
Std enthalpy of formation (ΔfHo298)	−168.5–−167.3 kJ mol−1
Std enthalpy of combustion (ΔcHo298)	−3.51506–−3.51314 MJ mol−1
Hazards
EU classification (DSD)	F+ N
R-phrases	R12, R51/53
S-phrases	(S2), S16, S33
NFPA 704	4 1 0
Related compounds
Related alkanes	2,2-Dimethylbutane 2,3-Dimethylbutane Triptane Tetramethylbutane
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Neopentane, also called 2,2-dimethylpropane, is a double-branched-chain alkane with five carbon atoms. Neopentane is a flammable gas at room temperature and pressure which can condense into a highly volatile liquid on a cold day, in an ice bath, or when compressed to a higher pressure.

Neopentane is the simplest alkane with a quaternary carbon, and has achiral tetrahedral symmetry. It is one of the three structural isomers with the molecular formula C₅H₁₂ (pentanes), the other two being n-pentane and isopentane. Out of these three, it is the only one to be a gas at standard conditions; the other being liquids.

The traditional name neopentane was still retained in the 1993 IUPAC recommendations, but is no longer recommended according to the 2013 recommendations. The preferred IUPAC name is the systematic name 2,2-dimethylpropane, but the substituent numbers are superfluous because it is the only possible “dimethylpropane.”

A neopentyl substituent, often symbolized by "Np", has the structure Me₃C-CH₂- for instance neopentyl alcohol (Me₃CCH₂OH or NpOH). As Np also symbolises the element neptunium (atomic number 93) one should use this abbreviation with care.

The obsolete name tetramethylmethane is also used, especially in older sources.

The boiling point of neopentane is only 9.5 °C, significantly lower than those of isopentane (27.7 °C) and normal pentane (36.0 °C). Therefore, neopentane is a gas at room temperature and atmospheric pressure, while the other two isomers are (barely) liquids.