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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07Nov 2012 by Vincent Summers 2 Comments

Why Urine is Yellow

Chemistry
[caption id="attachment_3172" align="alignright" width="366"] A urine sample.[/caption] Admit it. You've always wondered why. Why is urine yellow? What chemical or chemicals are involved? Consider the primary red blood cell component, “heme.” Heme & Porphyrin Dorland’s Medical Dictionary for Health Consumers, 2007, informs us heme is “an iron compound of protoporphyrin which constitutes the pigment portion or protein-free part of the hemoglobin molecule.” Heme is the colorful portion (red) of our blood. Notice, in particular, the partial word in the definition, porphyrin. Recycling & Trash Red blood cells become old and need to be replaced. What happens to the old red blood cells? They are, first, consumed by macrophages in the blood. For the person who has his or her body intact, much of this occurs within the spleen. It also…
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11Jun 2012 by Vincent Summers 6 Comments

Mad Hatters, Felt, and Mercury

Chemistry, History
[caption id="attachment_2497" align="alignright" width="440"] Harry S. Truman Felt Fedora Hat - Image: National Park Service[/caption] Associated with the hat making business, how do felt and mercury produce mad hatters? Felt hats have been produced from small animal pelts since about the 14th century. During the 19th century, fur was removed from the skin using camel urine. Some hatters used their own urine, instead. The active ingredient in urine was nitrogen-rich urea. Why Urine? Those who used their own urine and were being treated for syphillis produced superior felt! This was due to the mercurous chloride (HgCl) they'd taken as medicine. Urine was replaced by orange-colored mercuric nitrate Hg(NO₃)₂. [caption id="attachment_19437" align="alignright" width="240"] Tertiary syphilis. A horrible disease, generally avoidable.[/caption] Mad Hatters The vats of solution and the drying process generated…
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