http://www.erowid.org/archive/rhodium/chemistry/chloroephedrine.reduction.html 1-Phenyl-1-chloro-2-methylaminopropane (I) didesoxyephedrine (II) another possible structures for didesoxyephedrine (III) benzylic monoradical (IV) 1-Phenyl-1-chloro-2-methylaminopropane hydrochloride (V) YIELD; As a preliminary, it was ascertained that the same yield of 10% desoxyephedrine is obtained with (I) when hydrogenated with zinc-copper and hydrochloric acid as Schmidt obtained with the bromine compound. In subsequent experiments only I was used. The zinc-copper couple was then replaced by zinc alone in one experiment, by alkali-activated aluminum in another. Zinc afforded about the same yield as zinc-copper, while aluminum did not react. Zn-Pd + HCl ---> 34 % Al-Pd + HCl ---> 44% H2-Pd + CH3COOH ---> 80-90% CaH2-Pd + HCl --->86% MECHANISM; It is immediately apparent that the most important competitive reaction in the hydrogenation with metal and acid is not the conversion of atomic to molecular hydrogen but the conversion of (I) to a hydrocarbon, which cannot be suppressed even by increasing the concentration of atomic hydrogen by the catalyst. The identity of the hydrocarbon was not established at this point. As will be reported below, propenylbenzene was identified as the primary product of the reaction, in conformity with Emde's report; whether, and to what extent, it is further hydrogenated to propylbenzene as reported by Schmidt, is irrelevant to the reactions of (I). This confirms the role of the metal, and we may interpret the findings reported above by the assumption that the zinc donates two electrons to the polar C-Cl and C-N bonds of (I), allowing the ions Cl- and CH3NH- to break away, and leaving the biradical PhC·HC·HCH3 behind which is propenylbenzene when the orbitals of the two odd electrons overlap to form a p electron pair. Hydrogen, on the other hand, is not metallic enough to break the slightly polar C-N bond but it can break the C-Cl bond which in (I) - a substituted benzyl chloride - is very highly polar. Consequently a benzylic monoradical (IV) is formed, which quickly combines either with a hydrogen atom to form desoxyephedrine, or, to a lesser extent, with another radical (IV) to form (II). To test this hypothesis, (I) was reacted with copper, an element even less metallic than hydrogen. It might be reasonably expected to yield the monoradical (IV) which, in the absence of atomic hydrogen, can only dimerize. The expectation was confirmed and the product obtained showed the properties Emde reports for didesoxyephedrine. This may be considered as evidence for structure (II) for desoxyephedrine which Emde had suggested without being able to prove it. EXPERIMENTAL; Propenylbenzene from (I) and zinc (V) 11 g and 6 g of anhydrous sodium carbonate were suspended in 20 ml. of ether. 30 ml. of water was added, and agitated. The aqueous layer was washed with ether, the united ether solutions dried quickly with magnesium sulfate and filtered. The filtrate was kept under a vacuum until the ether had evaporated. Then 5 g. of zinc dust was added. The mixture heated up spontaneously to ebullition, and the reaction was moderated by cooling. The resulting liquid had a pure hydrocarbon smell and boiled at 173°C uncorr.; (bp of propenylbenzene 176°C, of propylbenzene 159.5°C). The unsaturation test was positive. N and Cl test negative; yield 4.8 g. (81.5%). Didesoxyephedrine from (I) and copper A preliminary experiment gave no results when the technique of the reaction with zinc was followed. Apparently the copper does not react vigorously enough to establish good contact with the liquid. Therefore the following method was used, 6 g. of anhydrous sodium acetate was dissolved in 80 ml. of water, and 14.4 g. of (V) was dissolved in the acetate solution. (These are the actual conditions of Emde's hydrogenation which yielded both desoxyephedrine and didesoxyephedrine.) Then 6 g. of copper powder was added and the mixture mechanically stirred during 12 hours. Excess alkali was added and the mixture distilled with steam to hydrolyze unreacted (I), and to remove all possible volatile products (ephedrine, pseudoephedrine etc.). The residue was extracted with ether, the ether extract dried with magnesium sulfate. A yellow oil remained which crystallized slowly, yield 3.1 g (32%), mp 71°C (Emde reports 70°C). insoluble precipitate with mercuric chloride in HCl solution (Emde reports the same). The low yield was apparently due to incomplete reaction, since large amounts of copper also were found unreacted.