Trimethyl orthoformate

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Trimethyl orthoformate[1]
Structural formula
Ball-and-stick model
CAS number 149-73-5 YesY
PubChem 9005
ChemSpider 8655
Jmol-3D images Image 1
Molecular formula C4H10O3
Molar mass 106.12 g mol−1
Appearance Colorless liquid
Density 0.97 g/mL
Melting point -53 °C
Boiling point 101–102 °C
S-phrases S9 S16 S26
Flash point 13 °C (55 °F; 286 K)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Trimethyl orthoformate is the simplest orthoester. It is a reagent used in organic synthesis for the introduction of a protecting group for aldehydes. The product of reaction of an aldehyde with trimethyl orthoformate is an acetal. In general cases, these acetals can be deprotected back to the aldehyde by using hydrochloric acid.

The industrial synthesis of this chemical is from hydrogen cyanide and methanol.[2]

Trimethyl orthoformate is a useful building block for creating methoxymethylene groups and heterocyclic ring systems. It introduces a formyl group to a nucleophilic substrate, e.g. RNH2 to form R-NH-CHO, which can undergo further reactions. It is used in the production of the fungicides, azoxystrobin and picoxystrobin, as well as for some members of the floxacin family of antibacterial drugs. A number of pharmaceutical intermediates are also made from trimethyl orthoformate.[2]


  1. ^ Trimethyl orthoformate at Sigma-Aldrich
  2. ^ a b Ashford's Dictionary of Industrial Chemicals, Third edition, 2011, ISBN 978-0-9522674-3-0, page 9388