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Matthias Eduard Schweizer is a Swiss chemist best-known for his work regarding cellulose in cuprammonium solutions and the creation of Schweizer's reagent.

Life and Academic Career

Matthias Eduard Schweizer was born on August 18, 1818 at Wila in Canton Zurich. His older brother, Kaspar Gottfried Schweizer, was a well-known astronomer.

Eduard Schweizer began studying natural science in Zurich and remained at the University of Zurich during his entire academic career. He began as an assistant to Karl Jakob Löwig, the first chair of the Department of Chemistry at the University of Zurich. His early lectures, based on knowledge gained during mining trips to Germany, focused on chemical technology and mineralogy. Later in his career, Schweizer was promoted to the post of Associate Professor, lectured in natural sciences at the Obere Industrieschule in Zurich until 1855, and continued his research in chemistry. He died on October 23, 1860 in Zurich.

Work and Discoveries

Early Work in Chemistry

Schweizer dabbled in several fields of chemistry including mineralogy, inorganic chemistry, and organic chemistry.

His work in mineralogy included many chemical analyzes of mineralogical substances with origins from various locations in Europe. He analyzed porphyry from Bad Kreuznach, Germany; manganese silicates from Tinzen, Switzerland; and ash from the eruption of Mount Gunter. Schhweizer also studied the newly-discovered mineral antigorite--a member of the serpentine group that was first found in Piedmont, Italy.

Schweizer also made several significant contributions to inorganic chemistry. He analyzed borates and chromates, studied the effects of acids on borax, and investigated the action of various bases and acids on potassium antimonyl tartrate. While working with chromates, Schweizer used carbon dioxide in combination with other weak acids to produce potassium dichromate from potassium chromate. He used similar methods to synthesize double salts of potassium from the chromates of magnesium and calcium.

Fig. 1: Structure of pyroxanthine

Schweizer’s organic research included the analysis of numerous plant products including methanol (wood alcohol) and xylitol. He studied the formation of carvacrol from carvone and thuja oil, discovered thujone, and isolated pyroxanthine (Fig. 1) from the dry distillation of wood.

Discovery of Schweizer's Reagent

Fig. 2:Synthesis of tetraaminecopper(II) dithionate

Fig. 3: Synthesis of tetraaminecopper(II) dithionate and tetraaminecopper(II) hydroxide

Schweizer's eventual discovery of his reagent, tetraaminediaquacopper(II) dihydroxide, began with his study of metal-amines and coordination chemistry. He created tetraaminecopper(II) dithionate from tetraaminecopper(II) sulfate hydrate and barium dithionate in acidic solution. (Fig. 2) In a subsequent experiment, Schweizer sought to synthesize tetraaminecopper(II) hydroxide by adding aqueous ammonia to freshly-prepared copper(II) dithionate, which produced a blue solution found "to dissolve plant fiber at ordinary temperature." This produce contained tetraaminecopper(II) dithionate as well as Schweizer's reagent, tetraaminecopper(II) hydroxide or [Cu(NH₃)₄](OH)₂. Schweizer found that the solution also dissolved paper, linen, silk, and wool.

Dissolution of Cellulose in Cuprammonium Solutions

Chemistry of Cuprammonium Reactions

Since then, studies have shown that Schweizer’s reagent is such a strong solvent of cellulose because it interacts with the hydroxyl groups on C2 and C3 of the glucose monomers. The binding process is initiated by the formation of a complex between the copper centers and the glucosic hydroxyl groups. This complex formation lowers the pKa of the hydroxyl groups, which allows the surrounding basic medium to remove a proton. (Fig. 4)

Fig. 4: Dissolution of cellulose in tetraaminecopper(II) hydroxide

Development of Cuprammonium Processes

Schweizer's discovery that cellulose dissolves in ammoniacal copper oxide solution, now called cuprammonium solution, served as the basis of the work of several other chemists and underpinned the synthetic fiber industry. Sir William Crookes used a cuprammonium solution to create a light bulb filament in 1881. Later, in 1890, Louis Henri Despeissis successfully produced fibers by dissolving cellulose in a cuprammonium hydroxide solution, removing impurities such as fats, and then precipitating filaments in a dilute acid solution. While the Despeissis process was unsuccessful in producing artificial fibers on an industrial scale, it was the first of several processes relying upon cuprammonium solutions in the production of synthetic fibers that could be used in fabric production. Throughout the twentieth century, several firms used cuprammonium processes to produce rayon; however, Asahi Chemical Industries Company is the only remaining manufacturer using this process as other manufacturers use the viscose process.

In addition to the production of synthetic fibers, the dissolution of cellulose in cuprammonium solutions remains useful in determining the presence of cellulose in various substances including cell walls.