Title: Angelic Acid
CAS Registry Number: 565-63-9
CAS Name: (Z)-2-Methyl-2-butenoic acid
Additional Names: cis-2-dimethylcrotonic acid; 2-methylisocrotonic acid; cis-2,3-dimethylacrylic acid
Molecular Formula: C5H8O2
Molecular Weight: 100.12
Percent Composition: C 59.98%, H 8.05%, O 31.96%
Literature References: Stereoisomer of tiglic acid. Found in ester form in sumbul root, Angelica archangelica L., Umbelliferae and together with tiglic acid esters in the oil of the Roman camomile, Anthemis nobilis L., Compositae. Isoln from seeds of Schoenocaulon officinale (Lindl.) A. Gray, Liliaceae (cevadilla seeds) by alkaline hydrolysis of cevadine: Stoll, Seebeck, Helv. Chim. Acta 35, 1275 (1952). Synthesis by trans addition of bromine to tiglic acid: Buckles, Mock, J. Org. Chem. 15, 680 (1950). Review and bibliography: Buckles et al., Chem. Rev. 55, 659 (1955).
Properties: Monoclinic rods, needles, plates; mp 45°. Spicy odor. Vesicant. d447 0.983. bp760 185°; bp12 86°. Sublimes. Volatile with steam. nD47 1.4434. pK (25°) 4.30. uv max (H2O): 217 nm (e 5.15 ´ 103). Molar heat of combustion 626.6 kcal. Sparingly soluble in cold water, freely sol in hot water. Sol in alcohol, ether. Prolonged boiling of aq soln causes isomerization to tiglic acid; the process is speeded up by traces of bromine and sunlight, also by strong mineral acids or alks. Dry crystals of angelic acid have been stored in bottles for years without evidence of isomerization.
Melting point: mp 45°
Boiling point: bp760 185°; bp12 86°
pKa: pK (25°) 4.30
Index of refraction: nD47 1.4434
Absorption maximum: uv max (H2O): 217 nm (e 5.15 ´ 103)
Density: d447 0.983
Derivative Type: Calcium salt dihydrate
Molecular Formula: Ca(C5H7O2)2.2H2O
Molecular Weight: 274.32
Percent Composition: Ca 14.61%, C 43.78%, H 6.61%, O 34.99%
Properties: Leaflets. Much more soluble in water than calcium tiglate: 100 parts of aq soln satd at 17.5° contains 23 parts of anhydr calcium angelate.
Derivative Type: Amide
Molecular Formula: C5H9NO
Molecular Weight: 99.13
Percent Composition: C 60.58%, H 9.15%, N 14.13%, O 16.14%
Properties: Crystals, mp 127-128°.
Melting point: mp 127-128°
Derivative Type: Methyl ester
Molecular Formula: C6H10O2
Molecular Weight: 114.14
Percent Composition: C 63.14%, H 8.83%, O 28.03%
Properties: Liquid; d420 0.9413; bp764 128°; nD20 1.4321.
Boiling point: bp764 128°
Index of refraction: nD20 1.4321
Density: d420 0.9413
Derivative Type: Ethyl ester
Molecular Formula: C7H12O2
Molecular Weight: 128.17
Percent Composition: C 65.60%, H 9.44%, O 24.97%
Properties: Liquid; d419.5 0.9178; bp760 141.5°, bp11 49°. nD20 1.4304. Heat of formn at constant vol 963.1 kcal, at constant press. 964.2 kcal.
Boiling point: bp760 141.5°; bp11 49°
Index of refraction: nD20 1.4304
Density: d419.5 0.9178
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