How Does
Introduction
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While many potent zero-calorie sweeteners are found in nature (e.g., Stevia plant), the majority of sweeteners sold today are made artificially. Only one of the main artificial sweeteners, sucralose ("Splenda"), is created from an actual carbohydrate. The other two, saccharin ("Sweet & Low") and aspartame ("Equal"), are created through fairly complicated chemical syntheses.
Sucralose ("Splenda")
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Sucralose synthesis.
The process starts by dissolving regular table sugar ("sucrose") in a solution of water and acetic acid (C₂H...O). The acetate anion bonds to the oxygen molecule in the "6"-position (i.e., the sixth carbon in the molecular ring) of the sucrose molecule. By attaching to the sucrose molecule at this particular position, the acetate anion serves as a "protecting group," which prevents certain active portions of the sucrose molecule from reacting with reagents in the next step.
Once the acetate-protecting group is in place, the modified sucrose molecule is combined with phosphorous oxychloride (PCl...) and a special catalyst. The powerfully reactive chloride ions quickly replace three -OH groups on the sucrose.
Finally, sodium hydroxide (NaOH) is added to raise up the pH of the solution, which terminates the PCl... reaction and breaks the acetate group off the molecule, restoring the original -OH group to the 6-position. The result is Sucralose.
Saccharin ("Sweet & Low")
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Saccharin synthesis.
The synthesis begins with anthranilic acid, which is basically a benzene molecule with a carboxylic acid group (-COOH) and an amine group (-NH₂) attached to adjacent carbons. First, the anthranilic acid is mixed with concentrated solution of nitrous acid (HNO₂) to replace the (-NH₂) group with a (-OH) group. After neutralizing the nitrous acid, sulfur dioxide (SO₂) gas is bubbled up through the solution, where it dissolves to form sulfous acid (H₂SO₃) and react with the target molecule to replace the (-OH) group with a (-SO₂) group. Next, chlorine (Cl₂) gas is bubbled up through the solution, forming hydrochloric acid (HCL) and causing the (-OH) group on the carboxyl group to get replaced by a chloride ion. Finally, ammonia (NH₃) is added to the solution, neutralizing the acidic pH and knocking the chlorine anion away with a powerful NH₂ anion. As a result, the sulfur and nitrogen atoms form a bond that completes the ring.
Aspartame ("Equal")
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Aspartame synthesis.
Two bacteria, genetically modified to produce the amino acids L-aspartic acid and L-phenylalanine, are incubated in separate culture dishes. Note: the "L" prefix specifies which "stereoisomer" of the molecule the compound is. Basically, stereoisomerism occurs in organic (i.e., carbon-based) molecules and has to do with the order in which the four atoms bonded to a carbon atom are oriented to one another.
As the bacteria multiply, they produce more and more L-aspartic acid/ L-phenylalanine. Once enough has been created, scientists transfer the contents of the grow chambers into centrifuges to separate the amino acids from the bacteria. The centrifuged amino acids are then passed along an ion-exchange column to purify the mixture into pure L-aspartic acid and L-phenylalanine, respectively.
L-phenylalanine is treated with methanol and undergoes an "ester" reaction, creating a bond between the "-OCH₃" anion and the carboxyl group (-COOH) while producing H₂O as a side product. The modified L-phenylalanine is then mixed with the L-aspartic acid and allowed to sit for 24 hours. Then temperature is then increased to 65 degrees Celsius for another 24 hours before being cooled to -18 degrees Celsius, which causes crystals to form.
These crystals are dried and mixed in a solution of acetic acid in a large tank with a palladium catalyst at the bottom. For the next 12 hours, hydrogen gas is slowly bubbled up into the solution.
Finally, the solution is filtered and dried. The resulting crystals are aspartame.
eHow Article: How Is Sweetener Made?
