27Dec 2012 by Vincent Summers 1 Comment

Forming Nitrogen Heterocycles from Aliphatic Amino Acids

Chemistry
How are nitrogen heterocycles formed from aromatic amines? Aliphatic hydrocarbons¹ take a number of forms. The simplest is written CH₃(CH₂)nCH₃, where n is a positive integer.²  Replace a hydrogen atom at one end of the chain with a carboxylic acid group (-COOH) and a hydrogen atom at the other end with an amino group (-NH₂), and you have a straight chain amino acid. For instance, choose n = 3. That gives the molecule HOOC-CH₂-CH₂-CH₂-CH₂-NH₂ Its name is 5-aminopentanoic acid or 5-aminovaleric acid. Cyclization Under the right conditions, this species can be cyclized to form an amine salt. The salt is then converted to a cyclic amide, a delta lactam. The lactam is next reduced to the amine piperidine. The overall process is illustrated in Fig. 1. Nitrogen Heterocycles A cyclic…
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26Dec 2012 by Vincent Summers 2 Comments

Organic Chemistry: Pericyclic Reactions

Chemistry
In chemistry, many reactions are simple, intuitive, and straight forward. Others can fool the uninformed. Organic pericyclic reactions are included among the latter. To illustrate this, we consider two reactions. The first is a simple esterification reaction, leading to the obvious product. The second is a pericyclic reaction. The Esterification Reacting an alcohol with a carboxylic acid generally produces a simple ester. So in the presence of a dehydrating agent, one can react ethyl alcohol with acetic acid, to get the ester ethyl acetate plus water. CH₃COOH + HO-C₂H₅ → CH₃COO-C₂H₅ + H₂O Organic Pericyclic Reactions CH₃-CH=CH-CH=CH-CH=CH-CH₃ → two possible ring structures The illustration in Fig. 1 shows a straight chain organic hydrocarbon converting into one of two cyclic structures, depending upon the source of energy. The input energy, whether heat…
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14Dec 2012 by Vincent Summers No Comments

Aromatic Tropylium Ion

Chemistry
[caption id="attachment_20212" align="alignright" width="440"] Aromatic tropylium cation[/caption] Aromatics are separate category of organic compounds. Often aromatic compounds are electrically neutral. However, a few do carry a charge. They are ions.¹ In fact many aromatic ions would not be aromatic if they lost their charge. We will consider the aromatic tropylium cation in this article. Three Carbon Atoms The smallest aromatic ion is the cyclopropenyl cation. The neutral cyclopropene molecule possesses 4 π-electrons. That is not an aromatic number. By making it a cation, it loses 2 of them, meeting the qualification for aromatic compounds.¹ [caption id="attachment_16191" align="alignright" width="240"] Spacefill Model.[/caption] Four Carbon Atoms On the basis of π-electron count alone, one might suppose a cyclobutadienyl di-anion or a cyclobutadienyl di-cation, would display aromaticity. That is not the case. There are…
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03Dec 2012 by Vincent Summers No Comments

Why Balloons Blow Up Round

Physics
[caption id="attachment_13619" align="alignright" width="440"] Balloons.[/caption] When you blow up latex balloons and build up some pressure in them, unless they are especially made to become some other shape, they tends toward roundness—they assume a spherical shape. Balloons blow up round! Why does it do that? Let’s look at the simple math and physics of the thing. Stretching Requires Force Take an ordinary piece of burst balloon and pull on it with your fingers. It takes a definite force to accomplish that, doesn’t it? And the task becomes more difficult the more you stretch it. We call the exertion “force.” It takes force to stretch the rubber. Since the required force becomes greater the more you stretch the skin of balloons, it is clear the more air you blow into them,…
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03Dec 2012 by Vincent Summers No Comments

Why are Some Bananas Sweeter than Others

Food
Some bananas are sweeter than others. How is that? Having purchased the golden fruit many times, I asked myself, why are some bananas sweeter than others? You pick up a bunch of small, curly, bright yellow fruits.¹ You take them home. On the way, you remove the one with the label. You peel it most of the way down. With a few quick bites, you finish it off. You go shopping again. Displayed are large, straight bananas. You note some bananas are sweeter, while others are starchier. Banana Varieties Each variety of banana is grown for a specific end use. Some (plantains) are fried in a skillet. They are starchy. Others are raised for sweetness and aroma. Those are called dessert bananas. The most popular form of dessert banana is…
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