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3,4-Dihydropyran (DHP) is a heterocyclic compound with the formula C5H8O. The six-membered C5O ring with the unsaturation adjacent to oxygen. The isomeric 3,6-dihydropyran has a methylene separating the double bond and oxygen. DHP is used for protecting group for alcohols. It is a colorless liquid.[1]

3,4-dihydropyran skelet
IUPAC names
Other names
2,3-Dihydro-4H-pyran, DHP
3D model (JSmol)
ECHA InfoCard 100.003.465
EC Number 203-810-4
UN number 2376
Molar mass 84.118 g·mol−1
Appearance Colorless liquid
Density 0.922 g/mL
Melting point −70 °C (−94 °F; 203 K)
Boiling point 86 °C (187 °F; 359 K)
GHS pictograms The flame pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)The exclamation-mark pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
H225, H315, H317, H319
P210, P233, P240, P241, P242, P243, P261, P264, P272, P280, P302+352, P303+361+353, P305+351+338, P321, P332+313, P333+313, P337+313, P362, P363, P370+378, P403+235, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references



Dihydropyran is prepared by the dehydration of tetrahydrofurfuryl alcohol over alumina at 300–400 °C.[2] THFA is itself prepared from tetrahydro-2-furoic acid.



In organic synthesis, the 2-tetrahydropyranyl (THP) group is used as a protecting group for alcohols.[3][4] Reaction of the alcohol with DHP forms a THP ether, protecting the alcohol from a variety of reactions. The alcohol can later be restored by acidic hydrolysis, concomitant with formation of 5-hydroxypentanal.[5]

Protection of alcohol as THP ether followed by deprotection. Both steps require acid catalysts.

See alsoEdit


  1. ^ Paul Ch. Kierkus (2001). "3,4‐Dihydro‐2H‐pyran". eEROS. doi:10.1002/047084289X.rd230.CS1 maint: Uses authors parameter (link)
  2. ^ R. L. Sawyer and D. W. Andrus (1955). "2,3-Dihydropyran". Organic Syntheses.; Collective Volume, 3, p. 276
  3. ^ R. A. Earl L. B. Townsend (1990). "Methyl 4-Hydroxy-2-butynoate". Organic Syntheses.; Collective Volume, 7, p. 334
  4. ^ Arthur F. Kluge (1990). "Diethyl [(2-Tetrahydropyranyloxy)methyl]phosphonate". Organic Syntheses.; Collective Volume, 7, p. 160
  5. ^ Wuts, Peter G. M.; Greene, Theodora W. (2006). "Protection for the Hydroxyl Group, Including 1,2‐ and 1,3‐Diols". Greene's Protective Groups in Organic Synthesis (4th ed.). pp. 16–366. doi:10.1002/9780470053485.ch2. ISBN 9780470053485.