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IUPAC name
2-α-Hydroxypropyl-piperidine; (1R)-1-[(2S)-2-piperidyl]-1-propanol
3D model (JSmol)
Molar mass 143.23 g·mol−1
Melting point 121 °C (250 °F; 394 K)
Boiling point 226 °C (439 °F; 499 K)
Solubility in ethanol good
Solubility in chloroform good
Solubility in diethylether moderate
+10° (natural)
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

Conhydrine is a poisonous alkaloid found in poison hemlock (Conium maculatum) in small quantities.

Isolation and properties[edit]

This oxygenated alkaloid was isolated by Wertheim from C. maculatum.[1] It crystallises in colourless leaflets, has a coniine-like odour, can be sublimed, and is strongly basic. It crystallises readily from ether. The salts are crystalline; the aurichloride small rhombs or prisms, mp. 133 °C; the benzoyl derivative mp. 132 °C.


On oxidation with chromic acid, conhydrine yields L-piperidyl-2-carboxylic acid.[2] It is converted into L-coniine either by reduction of the iodo-derivative (iodoconiine), C8H16IN, formed by the action of hydriodic acid and phosphorus at 180 °C[3][4][5] or by hydrogenation of the mixture of coniceines produced, when it is dehydrated by phosphorus pentoxide in toluene.[6]


These and other observations indicate that the oxygen atom must occur as a hydroxyl group, in the n-propyl side chain in either the α- or β-position, since the γ-position would involve the production of piperidyl-2-propionic acid on oxidation. 2-β-Hydroxypropyl-piperidine suggested by Willstätter[2] seemed to be excluded, since neither of the two forms of this product prepared by Löffler and Tschunke[7] resembled conhydrine, and these authors suggested the α-position as probably representing the alkaloid. Support for this view was provided by Hess and coworkers[8][9][10] ,[11][12] who showed that DL--N-methylconhydrone is N-methyl-2-piperidyl ethyl ketone, that DL-conhydrine (mp. 69–70 °C), produced by a somewhat indirect method, is identical with the product, mp. 69.5–71.5 °C, prepared by Engler and Bauer[13][14] by the reduction with sodium in ethyl alcohol of 2-pyridyl ethyl ketone, and that conhydrine on dehydrogenation over platinum or palladium asbestos gives rise to a mixture of tetrahydropyridyl 2-ethyl ketone and 2-α-hydroxypropyl-pyridine. Späth and Adler[6] have shown that conhydrine can be degraded in two stages by exhaustive methylation to trimethylamine, and a mixture of two products, an oil, C8H14O, bp. 157–159 °C@744 mmHg, and a crystalline substance, C8H16O2, mp. 75–76 °C. The oil, when heated with water at 170 °C is converted, by addition of a molecule of water, into the crystalline substance. The latter contains two active hydrogen atoms (Zerewitinoff estimation), and on exposure to hydrogen over Pd/C absorbs enough to saturate one double bond producing a new substance, mp. 94–96 °C. On oxidation with permanganate in dilute sulfuric acid, propionaldehyde and succinic acid are produced, whilst the saturated substance, mp. 94–96 °C, is oxidised to n-valeric acid. These results indicate that the substance of mp. 75–76 °C is εζ-dihydroxy-Δα-n-octene, that the oil, C8H14O, is the corresponding oxide, and that the representation of conhydrine as 2-α-hydroxypropyl-pyridine accounts for their production.


  1. ^ Wertheim, Th. (1856). "Ueber ein neues Alkaloïd in Conium maculatum". Annalen der Chemie und Pharmacie. 100 (3): 328–339. doi:10.1002/jlac.18561000311. 
  2. ^ a b Willstätter, Richard (1901). "Oxydation des Conydrins". Berichte der Deutschen Chemischen Gesellschaft. 34 (2): 3166–3171. doi:10.1002/cber.190103402290. 
  3. ^ Hofmann, A. W. (1885). "Zur Kenntniss der Coniin-Gruppe". Berichte der Deutschen Chemischen Gesellschaft. 18 (1): 5–23. doi:10.1002/cber.18850180103. 
  4. ^ Lellmann, Eugen (1890). "Ueber die Coniceïne". Justus Liebig's Annalen der Chemie. 259 (2–3): 193–208. doi:10.1002/jlac.18902590205. 
  5. ^ Löffler, Karl; Friedrich, Gotthold (1909). "Die Synthese des β-Coniceins (l-α-Allyl-piperidin)". Berichte der Deutschen Chemischen Gesellschaft. 42 (1): 107–116. doi:10.1002/cber.19090420113. 
  6. ^ a b Späth, Ernst; Adler, Erich (1933). "Zur Konstitution des Konhydrins". Monatshefte für Chemie. 63 (1–2): 127–140. doi:10.1007/BF01522210. 
  7. ^ Löffler, Karl; Tschunke, Reinhold (1909). "Über die Konstitution des Conhydrins (optisch-aktives α-Äthyl-piperidyl-alkin)". Berichte der Deutschen Chemischen Gesellschaft. 42 (1): 929–948. doi:10.1002/cber.190904201153. 
  8. ^ Hess, Kurt; Eichel, Annaliese (1917). "Über die Alkaloide des Granatapfelbaumes. IV. Ein Trennungsgang für die Reindarstellung der Pelletierin-Alkaloide. Aufklärung der Konstitution des Methyl-isopelletierins (Methyl-pelletierin, Isomethyl-pelletierin). Umwandlung des Conhydrins in Methylisopelletierin. Die Konstitution des Conhydrins". Berichte der Deutschen Chemischen Gesellschaft. 50 (2): 1386–1407. doi:10.1002/cber.19170500239. 
  9. ^ Heß, Kurt (1919). "Über die Beziehung von Methyl-isopelletierin, d,l-Methyl-conhydrinon und (N-Methyl-piperidyl)-propan-1-on. Ein Isomeriefall von Verbindungen mit einem asymmetrischen dreiwertigen Stickstoffatom. VI. Mitteilung über die Alkaloide des Granatapfelbaumes". Berichte der deutschen chemischen Gesellschaft (A and B Series). 52 (5): 964–1004. doi:10.1002/cber.19190520513. 
  10. ^ Heß, Kurt; Weltzien, Wilhelm (1920). "Über die Fähigkeit der Pflanze, optische Antipoden aufzubauen". Berichte der deutschen chemischen Gesellschaft (A and B Series). 53 (2): 119–129. doi:10.1002/cber.19200530202. 
  11. ^ Hess, Kurt; Grau, Reinhold (1925). "Neue Umwandlungen von Conhydrin und Methylisopelletierin. (V. Mitteilung zur Frage des asymmetrischen dreiwertigen Stickstoffatoms)". Justus Liebig's Annalen der Chemie. 441 (1): 101–137. doi:10.1002/jlac.19254410106. 
  12. ^ Meisenheimer, Jakob; Mahler, Emil (1928). "Über das Methyl-isopelletierin. (VIII. Mitteilung zur Stereochemie des gesättigten dreiwertigen Stickstoffatoms)". Justus Liebig's Annalen der Chemie. 462 (1): 301–316. doi:10.1002/jlac.19284620119. 
  13. ^ Engler, C.; Bauer, F. W. (1891). "Ueber das α-Aethylpyridylketon und dessen Ueberführung in Pseudoconhydrin". Berichte der Deutschen Chemischen Gesellschaft. 24 (2): 2530–2536. doi:10.1002/cber.18910240244. 
  14. ^ Engler, C.; Bauer, F. W. (1894). "Die Reductionsproducte des α-Methylpyridylketons und die Nichtidentität des α-Aethyl-Piperylalkins mit dem activen Pseudoconhydrin". Berichte der Deutschen Chemischen Gesellschaft. 27 (2): 1775–1779. doi:10.1002/cber.189402702121.