Solid phase
Official name
alpha-Acetonitrile
Secondary names
Acetonitrile-LTM; alpha-CH3CN; CH3CN-II
CAS number
75-05-8
Type
Family
molecular solid
Class
polar molecular solid
Compound type
nitrile
Chemical composition
Formula
$\alpha-CH_3CN$
Chemical formula
CH3CN
Elemental formula
C2 H3 N
Isotope mixture type
terrestrial abundance
2.0
  Formula Name Family Number min-max Mole fraction Isotope mole fraction State Relevance
$CH_3CN$ Acetonitrile molecule 1 1.0 1 pure main
Chemical functions
  Function Number
$R-CH_3$ 1
$R-C \equiv N$ 1
Chemical bonds
  Bond Number
$\geq N \dots H-$ 2
$\geq C-H$ 3
$\equiv C-C\leq$ 1
$-C\equiv N$ 1
Class
molecular solids with polar molecules (02)
Type
with polyatomic organic polar molecules (CnHm...) (02.01)
Group
hydrocarbon with pnictogens (02.01.04)
Polymorphs
Phase name
alpha-acetonitrile (phase II)
Phase type
crystalline
Crystal system
monoclinic
Crystal class
prismatic
Crystal class symbol
2/m (C2h)
Crystal spacegroup
P2(1)/c
Molar mass
41.053 $g/mol$
Density
1.028 $g/cm^3$
State NTP
liquid
Phase transitions
Phase transition type Other phases Temperature - Pressure
solid-gas from gas forms by condensation between ~175 K and 216.9 K (~ -100°C and -56.2°C)
solid-solid to beta-CH3CN above 216.9 K (-56.2°C)
solid-solid from metastable beta-CH3CN above ~205K
Phase transitions comments
alpha-CH3CN is the low temperature phase but is not the one formed upon crystallization of amorphous ice (kinetically metastable phase). It forms by condensation at temperature above about 175K and from metastable beta phase at temperature above ~205K
Refringence type
biaxial
Refraction index $n_{\alpha}$
1.459 @ 140K
Pure color
colorless
Color
colorless
Diaphaneity
translucent
Luster
vitreous
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