2-Methylbut-3-yn-2-ol

2-Methylbut-3-yn-2-ol is the organic compound with the formula HC₂C(OH)Me₂ (Me = CH₃). A colorless liquid, it is classified as an alkynyl alcohol.

2-Methylbut-3-yn-2-ol

Names
Preferred IUPAC name 2-Methylbut-3-yn-2-ol
Other names Ethynylmethylcarbinol Dimethylethynylcarbinol 1,1-Dimethyl-2-propyn-1-ol Dimethylethynylmethanol MB Mebynol
Identifiers
CAS Number	115-19-5
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL3185871
ChemSpider	21106133
ECHA InfoCard	100.003.700
EC Number	204-070-5
PubChem CID	8258
RTECS number	ES0810000
UNII	EHB904XHKH
UN number	1987
CompTox Dashboard (EPA)	DTXSID2021949
InChI InChI=1S/C5H8O/c1-4-5(2,3)6/h1,6H,2-3H3 Key: CEBKHWWANWSNTI-UHFFFAOYSA-N
SMILES CC(C)(C#C)O
Properties
Chemical formula	C5H8O
Molar mass	84.118 g·mol−1
Appearance	Colorless liquid
Density	0.8637 g/cm3
Melting point	3 °C (37 °F; 276 K)
Boiling point	104 °C (219 °F; 377 K)
Solubility in water	good
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H226, H302, H315, H318, H319, H335, H361
Precautionary statements	P201, P202, P210, P233, P240, P241, P242, P243, P261, P264, P270, P271, P280, P281, P301+P312, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P312, P321, P330, P332+P313, P337+P313, P362, P370+P378, P403+P233, P403+P235, P405, P501
Flash point	20 °C (68 °F; 293 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation and use

It arises from the condensation of acetylene and acetone. The addition can be promoted with base^[1] (Favorskii reaction) or with Lewis acid catalysts.^[2] 2-Methylbut-3-yn-2-ol is produced on an industrial scale as a precursor to terpenes and terpenoids.

2-Methylbut-3-yn-2-ol is an intermediate in this industrial route to geraniol.^[3]

2-Methylbut-3-yn-2-ol also is used as a monoprotected version of acetylene. For example, after arylation at carbon, the acetone can be removed with base:^[4]

HC₂C(OH)Me₂ + ArX + base → ArC₂C(OH)Me₂ + [Hbase]X

ArC₂C(OH)Me₂ → ArC₂H + OCMe₂

In this regard, 2-methylbut-3-yn-2-ol is used similarly to trimethylsilylacetylene.