Structural Formula Vector Image
Title: a-Estradiol
CAS Registry Number: 57-91-0
CAS Name: (17a)-Estra-1,3,5(10)-triene-3,17-diol
Additional Names: 1,3,5-estratriene-3,17a-diol; 3,17-dihydroxyestratriene
Molecular Formula: C18H24O2
Molecular Weight: 272.38
Percent Composition: C 79.37%, H 8.88%, O 11.75%
Literature References: Has been isolated from pregnancy urine of mares. Prepn from b-estradiol by inversion of the hydroxyl group at C-17 after tosylation: Allais, Hoffmann, US 2835681 (1958).
Properties: Needles with ½H2O from 80% alcohol, mp 220-223°. [a]D20 +53 to +56° (c = 0.9 in dioxane). Not precipitated by digitonin (in 80% alcoholic soln). Soluble in alcohol, acetone, aq alkalies. One gram dissolves in more than 100 ml of boiling benzene. Slightly sol in ether, chloroform. Insol in water, aq dil acids.
Melting point: mp 220-223°
Optical Rotation: [a]D20 +53 to +56° (c = 0.9 in dioxane)
Derivative Type: Diacetate
Molecular Formula: C22H28O4
Molecular Weight: 356.46
Percent Composition: C 74.13%, H 7.92%, O 17.95%
Properties: mp 140-142°.
Melting point: mp 140-142°
Derivative Type: 3-Benzoate
Molecular Formula: C25H28O3
Molecular Weight: 376.49
Percent Composition: C 79.75%, H 7.50%, O 12.75%
Properties: mp 156-157°; also reported as polymorphous: I, mp 63°; II, mp 153°; III, mp 158°.
Melting point: mp 156-157°; also reported as polymorphous: I, mp 63°; II, mp 153°; III, mp 158°

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