11Aug 2019 by Vincent Summers 2 Comments

Tetrahydrofuran or Diethyl Ether – Which to Use?

Chemistry
Tetrahydrofuran (C4H8O) is a heterocyclic hydrocarbon. One of the carbon atoms of a cyclopentane ring (along with its two hydrogen atoms) is replaced by an atom of oxygen. THF is an ether. It's frequently used for its solvent properties. In certain organometallic reactions, tetrahydrofuran replaces all or part of the standard solvent diethyl ether, (C2H5-O-C2H5), written in chemists' shorthand Et-O-Et. Tetrahydrofuran Vs. Diethyl Ether Although THF is essentially diethyl ether gone cyclic, its physical properties differ somewhat. A prime example of that relates to hydrogen bonding. Although both molecules possess an electron-rich oxygen atom, in THF, the oxygen is openly exposed. The ring can twist, but that's about it. The hydrocarbon portions of ethyl ether¹ have much greater freedom of motion. They can sweep around, making hydrogen bonding easier to…
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14Apr 2019 by Vincent Summers 1 Comment

Crown Ether Donut Holes Serve Special Purposes

Chemistry
[caption id="attachment_23625" align="alignright" width="480"] Assorted Crown Ethers[/caption] Crown ethers are designer molecules – ring structures intended to serve specialized purposes. Each ring contains a number of ether linkages (-C-O-C-) that, based upon their structural formulas as they are drawn on paper, give the appearance of a royal crown. The “crowns” have different “sizes.” The most common crown ethers sport ethyleneoxy groups (-CH2-CH2-O-) joined end-to-end (making these structures oligomers), which are closed like a necklace. Ring properties and rigidity may be modified by means of appendages on the ring or other hetero atoms along the ring. Simple crown ether rings such as those shown in the figure lack rigidity because every bond is single. There are no multiple bonds reducing flexibility. Crown Ether Nomenclature For the most common crown ethers, there…
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22Mar 2014 by Vincent Summers 14 Comments

Why Sulfuric Acid Turns Sugar Black

Chemistry
Sugar is white. Sulfuric acid is colorless. So how is it sulfuric acid turns sugar black? Table sugar is actually two sugars in one—a disaccharide. It is commonly known as sucrose. Sucrose is a combination of fructose, a sugar found in fruits, and glucose, known also as blood-sugar, grape-sugar, and corn-sugar. Its chemical formula is C₁₂H₂₂O₁₁. The way these atoms are attached to each other by chemical bonds determines its structural formula. In the Left Corner… Most sugar from a grocery store is granular and pure white. If the grains are large enough—existing as large crystals—it is immediately apparent that sugar isn't even white; it is totally colorless and transparent. Sold at candy stores, we call it rock candy. [sc name="MidArticleAdsense"] In the Right Corner… Concentrated sulfuric acid is thick…
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