Penny le Couteur & Jay Burreson by Napoleon's Buttons: How 17 Molecules Changed History
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storage as the lesser branched amylopectin and unbranched amylose is sufficient for a plantâs lower metabolic rate. This small chemical difference, relating only to the number and not to the type of cross-link, is the basis for one of the fundamental differences between plants and animals.
The different branching in starch (amylose and amylopectin) compared with glycogen. The greater the branching, the greater the number of chain ends for enzymes to break down the linkages and the faster glucose can be metabolized.
CELLULOSE MAKES A BIG BANG
Although there is a very large amount of storage polysaccharide in the world, there is a lot more of the structural polysaccharide, cellulose. By some accounts half of all organic carbon is tied up in cellulose. An estimated 10 14 kilograms (about a 100 billion tons) of cellulose is biosynthesized and degraded annually. As it is not only an abundant but also a replenishable resource, the possibility of using cellulose as a cheap and readily available starting material for new products long interested chemists and entrepreneurs.
By the 1830s it was found that cellulose would dissolve in concentrated nitric acid and that this solution, when poured into water, formed a highly flammable and explosive white powder. Commercialization of this compound had to wait until 1845 and a discovery by Friedrich Schönbein of Basel, Switzerland. Schönbein was experimenting with mixtures of nitric and sulfuric acids in the kitchen of his home, against the wishes of his wife, who perhaps understandably had strictly forbidden the use of her residence for such activities. On this particular day his wife was out, and Schönbein spilled some of the acid mixture. Anxious to clean up the mess quickly, he grabbed the first thing that came to handâhis wifeâs cotton apron. He mopped up the spill and then hung the apron over the stove to dry. Before long, with an extremely loud bang and a great flash, the apron exploded. How Schönbeinâs wife reacted when she came home to find her husband continuing his kitchen experiments on cotton and the nitric acid mix is not known. What is recorded is what Schönbein called his materialâ schiessbaumwolle, or guncotton. Cotton is 90 percent cellulose, and we now know that Schönbeinâs guncotton was nitrocellulose, the compound formed when the nitro group (NO 2 ) replaces the H of OH at a number of positions on the cellulose molecule. Not all these positions are necessarily nitrated, but the more nitration on cellulose, the more explosive is the guncotton produced.
The structure of part of a cellulose molecule. The arrows show where nitration can take place at the OH on C#2, 3, and 6 of each of the glucose units
A portion of the structure of nitrocellulose or âguncottonâ showing nitration;âNO 2 is substituted for -H at every possible OH position on each glucose unit of the cellulose.
Schönbein, recognizing the potential profit from his discovery, established factories to manufacture nitrocellulose, hoping it would become an alternative to gunpowder. But nitrocellulose can be an extremely dangerous compound unless it is kept dry and handled with proper care. At the time the destabilizing effect of residual nitric acid on the material was not understood, and thus a number of factories were accidentally destroyed by violent explosions, putting Schönbein out of business. It was not until the late 1860s, when proper methods were found to clean guncotton of excess nitric acid, that it could be made stable enough for use in commercial explosives.
Later, control of this nitration process led to different nitrocelluloses, including a higher-nitrate-content guncotton and the lower-nitrate-content materials collodion and celluloid. Collodion is a nitrocellulose mixed with alcohol and water and was used extensively in early photography. Celluloid, a nitrocellulose mixed with camphor, was one of the first successful
The different branching in starch (amylose and amylopectin) compared with glycogen. The greater the branching, the greater the number of chain ends for enzymes to break down the linkages and the faster glucose can be metabolized.
CELLULOSE MAKES A BIG BANG
Although there is a very large amount of storage polysaccharide in the world, there is a lot more of the structural polysaccharide, cellulose. By some accounts half of all organic carbon is tied up in cellulose. An estimated 10 14 kilograms (about a 100 billion tons) of cellulose is biosynthesized and degraded annually. As it is not only an abundant but also a replenishable resource, the possibility of using cellulose as a cheap and readily available starting material for new products long interested chemists and entrepreneurs.
By the 1830s it was found that cellulose would dissolve in concentrated nitric acid and that this solution, when poured into water, formed a highly flammable and explosive white powder. Commercialization of this compound had to wait until 1845 and a discovery by Friedrich Schönbein of Basel, Switzerland. Schönbein was experimenting with mixtures of nitric and sulfuric acids in the kitchen of his home, against the wishes of his wife, who perhaps understandably had strictly forbidden the use of her residence for such activities. On this particular day his wife was out, and Schönbein spilled some of the acid mixture. Anxious to clean up the mess quickly, he grabbed the first thing that came to handâhis wifeâs cotton apron. He mopped up the spill and then hung the apron over the stove to dry. Before long, with an extremely loud bang and a great flash, the apron exploded. How Schönbeinâs wife reacted when she came home to find her husband continuing his kitchen experiments on cotton and the nitric acid mix is not known. What is recorded is what Schönbein called his materialâ schiessbaumwolle, or guncotton. Cotton is 90 percent cellulose, and we now know that Schönbeinâs guncotton was nitrocellulose, the compound formed when the nitro group (NO 2 ) replaces the H of OH at a number of positions on the cellulose molecule. Not all these positions are necessarily nitrated, but the more nitration on cellulose, the more explosive is the guncotton produced.
The structure of part of a cellulose molecule. The arrows show where nitration can take place at the OH on C#2, 3, and 6 of each of the glucose units
A portion of the structure of nitrocellulose or âguncottonâ showing nitration;âNO 2 is substituted for -H at every possible OH position on each glucose unit of the cellulose.
Schönbein, recognizing the potential profit from his discovery, established factories to manufacture nitrocellulose, hoping it would become an alternative to gunpowder. But nitrocellulose can be an extremely dangerous compound unless it is kept dry and handled with proper care. At the time the destabilizing effect of residual nitric acid on the material was not understood, and thus a number of factories were accidentally destroyed by violent explosions, putting Schönbein out of business. It was not until the late 1860s, when proper methods were found to clean guncotton of excess nitric acid, that it could be made stable enough for use in commercial explosives.
Later, control of this nitration process led to different nitrocelluloses, including a higher-nitrate-content guncotton and the lower-nitrate-content materials collodion and celluloid. Collodion is a nitrocellulose mixed with alcohol and water and was used extensively in early photography. Celluloid, a nitrocellulose mixed with camphor, was one of the first successful
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