New PDF release: A Short History of Chemistry

By Isaac Asimov

ISBN-10: 0385036736

ISBN-13: 9780385036733

From using metals through prehistoric guy to the alchemical experiments of medieval and renaissance guy to the complicated chemical talents of up to date guy, Asimov lines the improvement of this development block of our technological global.

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Pavine The reduction of papaverine with tin and hydrochloric acid affords 1,2,3,4-tetrahydropapaverine and a second base, pavine, 40 The Isoquinoline Alkaloids which is a secondary base having the composition of a dihydropapaverine. It is not identical with 3,4-dihydropapaverine and as it cannot be further reduced or oxidised back to papaverine can­ not be 1,2-dihydropapaverine. The structure (63) was originally assigned to pavine, but no veratric acid has ever been isolated from the products of oxidation of pavine as would be expected on the basis of such a structure.

MeON J \ (6) OMe xCOOH MeO. CH3 (7) 2 OMe thought to be derived. This view was strengthened by the pro­ duction of a dimethoxyphthalic acid, veratric acid and pyridine2,3,4-tricarboxylic acid (6) and papaverinic acid on oxidation of the alkaloid. The dimethoxyphthalic acid was initially believed to be identical with the then known hemipinic acid (7) and as it was initially supposed to arise from a unit of type (8) in papaverine the alkaloid was assigned the part-structure (9). The mild oxidation of papaverine results in the conversion of —CH 2 — to —CO— and this was interpreted on the basis of the structure (9) as oxidation of—CH 3 to —CHO and the product was named papaveraldine.

3. Fission of the molecule at the diphenyl ether link or links to give simple benzylisoquinolines whose structures and stereo­ chemistry can be determined. From the information provided by these reactions the structure of the fully methylated alkaloid may be assembled, and the positions of free hydroxyl groups in the alkaloid itself can be determined by repetition of some of the reactions using the ethyl instead of the Bisbenzylisoquinolines 43 44 The Isoquinoline Alkaloids methyl ether. The application of these methods of structure determination may be illustrated by reference to work on examples of each of the distinct series of bases set out in formulae (8)—(14).

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A Short History of Chemistry by Isaac Asimov

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