Chemistry Archives - Page 9 of 22

13Aug 2018 by Vincent Summers 1 Comment

Uranocene – The Trend Setting Aromatic Actinide Sandwich Compound

Uranocene, U(C₈H₈)₂, or biscyclooctatetraenyl uranium, is a most interesting aromatic organometallic sandwich compound.1 Notice its dumbbell-like shape. By no means is its shape uranocene's only claim to fame. But before we get into that, it would be helpful to explain terms. We can guess why it's an organometallic compound, just as we can guess why it's called a sandwich compound. Let us, however, discuss what we mean by the term aromatic. Aromaticity in a Nutshell An aromatic structure is a molecule or ion that is cyclic and flat and that incorporates 4n+2 conjugated (alternating) sp2 (double) bonds, where n is some small integer. It displays increased stability over non-aromatic structures. Despite possessing double bonds, aromatic structures tend to undergo substitution rather than addition reactions. It requires considerable energy to disrupt…

07Jul 2018 by Vincent Summers 1 Comment

Fireworks Chemistry – Start With a Bang, Add Some Color

Chemistry, Entertainment

Pyrotechnics, often called fireworks, has a long history dating back to the days of gunpowder (black powder), developed in 9th-century China. Whether it is a sizzle, an explosion, or a showy display of colorful lights and sounds, the chemical reactions involve oxidation/reduction (REDOX) chemistry. What Is Oxidation? Oxidation is essentially the removal of electrons. Consider a very simple example. An uncharged sodium atom (symbol: Na) has 11 negatively-charged electrons. The atom has no net charge, however, because in its center part or nucleus, there are 11 positively-charged protons. Sodium can lose one electron to form a positively-charged ion called a cation. Now we can look at this process as if it were a mathematical equation. If we have the number 4 and we wind up with the numbers 3 and…

16Jun 2018 by Vincent Summers No Comments

What Is Asparagusic Acid? Its Metabolites? A Funny Story

Chemistry, People

Many enjoy hot asparagus, whether as a cream soup, or a simple steamed, sautéed, or even raw vegetable. Since I am a chemist, I find it of interest from that perspective as well. Yes, I realize the reader almost certainly has already deduced asparagusic acid is named for this grass-related vegetable. Background But let me give a little background before I get into asparagus and asparagusic acid, and why I write concerning them. When I was the age for it, I attended Drexel Institute of Technology1 in Philadelphia, PA. Drexel offered the benefit of a cooperative work assignment each year to provide job-related experience plus a small income to help cover the cost of college. My first assignment provided an additional perquisite: a government car for transportation to Trenton, NJ.…

08Jun 2018 by Vincent Summers No Comments

The Fascinating Acetylacetone Molecule and Its Acetylacetonate Salts

Chemistry, Technology

[caption id="attachment_20255" align="alignright" width="400"] Cobalt III Acetylacetonate[/caption] Acetylacetone is the simplest of the β-diketones and supports the phenomenon we call keto-enol tautomerism (see the illustration). Notice that the third carbon atom in the 5-carbon keto chain loans one of its hydrogen atoms in forming the enol tautomer. The freedom to move of this hydrogen atom suggests acetylacetone is a weak acid.1 In effect, the saturated di-ketone becomes an unsaturated di-alcohol. Only instead of two hydrogen atoms, one to each oxygen atom, there is just the one hydrogen atom that must be shared. Preparation Commercially, acetylacetone or H(acac) can be prepared from isopropenyl acetate by heating it in the presence of an appropriate metal catalyst. Dissociation and Reaction Since it is an acid, it can ionize or "disassociate", giving a positive…

23May 2018 by Vincent Summers 4 Comments

Tylenol, Its Structure, Nomenclature, and a Lab Synthesis

Chemistry, Medicine

Tylenol® is a trade name for acetaminophen.1 Does the latter word sound foreign to you? Let's find out what it means. This compound contraction combines acetyl with amino with phenol. What's in a Name? Does acetyl remind you of acetic acid or vinegar? Acetic acid is CH3COOH. The acetyl group is written CH3CO–. Amino is familiar too, as in amino acid? The basic amino group is written NH2–, though at times one or both of the hydrogen atoms are replaced by something else, as it is for Tylenol. Finally, "phen" stands for phenyl. Remove one atom from a benzene ring and you have phenyl. C₆H₅– is the simplest phenyl ring. Again, hydrogen atoms may be replaced with something else. The end result of putting these together to form acetaminophen is…

27Apr 2018 by Vincent Summers 1 Comment

How the Tear Ingredient Lysozyme Fights Bacteria

Biology, Chemistry

[caption id="attachment_19802" align="alignright" width="460"] 1,4-beta glycosidic bond[/caption] Human tears largely consist of water, sodium, and potassium electrolytes. However, these are not the only important substances found in tears. There are a number of complex organic substances essential in maintaining the eye. One ingredient is lysozyme, prominent among a group of chemicals which exhibit antibacterial behavior [see the PubChem reference for an image of lysozyme]. Lysozyme Modus Operandum The University of Colorado reference (cited) makes the following statement: "The enzyme lysozyme breaks down bacterial cell walls, which are made of a unique compound called peptidoglycan." Molecular Structure of the Contenders [caption id="attachment_19810" align="alignright" width="330"] cyclohexane chair conformer[/caption] The fifty-cent name for lysozyme is N-acetylmuramide glycanhydrolase. The suffix at the end of the name, -ase, indicates this compound is an enzyme. An…

11Apr 2018 by Vincent Summers 4 Comments

Cooking Onions: Flavor Chemistry Changes

Chemistry, Food

[caption id="attachment_21597" align="alignright" width="480"] M-m-m, Sweet![/caption] An onion, particularly a yellow or Bermuda onion possesses a strong, perhaps acrid flavor. And its aroma? You are likely to weep when you chop one! Yet, if you take that same onion and fry it, it can be just as fragrant and sweet as ever you could wish. What happened? It's a matter of chemistry. From Wild to Tame The flavor of a raw onion is the product of a number of complex organic substances. The ingredient primarily responsible for tear-ing, is (Z)-propanethial-S-oxide. This compound, a lachrymator (tear-producing gas), is produced when onion cell walls are broken by slicing and chopping. Does frying result in a decrease of this chemical, resulting in sweetness? Does this compound decompose on frying to producing the sweetness?1…

05Mar 2018 by Vincent Summers No Comments

Acid-Base and REDOX (Oxidation-Reduction) Chemical Reactions

Chemistry

[caption id="attachment_19477" align="alignright" width="440"] Rocketry thrives due to REDOX reactions.[/caption] Acid-Base and Redox: When they can, chemists categorize chemical reactions into types. Some specialized varieties of chemical reaction include those named for specific individuals involved in their discovery. As examples, there are the Diels-Alder reaction, the Claisen rearrangement, the Dieckmann condensation, and the Friedel-Crafts alkylation. Yet, many chemical reactions can be classified simply as acid-base reactions, or as oxidation-reduction (REDOX) reactions. Consider examples of each... Acid-Base Reactions When I was young, I was deeply interested in rocketry. My parents bought me one of those red plastic rockets that included a pump. You partly filled the rocket with water, then pumped air into it until the pressure made it difficult to pump more. Then you aimed it upward and pushed a…

13Feb 2018 by Vincent Summers No Comments

Is Cyclopropenethione Aromatic, As Is Its Oxygen Analog?

Chemistry, Logic

As small as it is, and even with a heteroatom in its make up, cyclopropenethione is aromatic, in the same way cyclopropenone is aromatic. Its aromaticity is not due to a theoretically electrically neutral structure, as in Figure 1, but to its "alternative" zwitterionic structure, shown in Figure 2. Aromatic Characteristics Hückel descriptors fall short of aromaticity if cyclopropenethione exhibited only the structure drawn in Figure 1. In addition to a closed and flat ring, aromaticity requires a 4n+2 number of π-electrons (pi), where n is usually a small integer. In the un-ionized form of Figure 1, each carbon atom has a π-electron, for a total of 3 electrons. This is because every double bond consists of one π-electron plus one σ-electron (sigma) per constituent atom. Widening Perspectives: Cyclopropenethione The…

10Feb 2018 by Vincent Summers 9 Comments

Shampoo – Is It Soap, Is It Detergent, or What?

Chemistry, Health

Shampoos are hair-care products meant to clean hair while allowing it to remain manageable. Is shampoo soap, detergent, or what? Individual shampoo products may contain many different ingredients to impart additional characteristics, but largely mainstream shampoos consist of two combined surfactants. Sodium laureth sulfate or sodium lauryl sulfate is the main surfactant. Cocamidopropyl betaine is the secondary surfactant. We will consider these two ingredients in answering the title question. Sodium Lauryl Sulfate Sodium lauryl sulfate (also called sodium dodecyl sulfate) is an anionic surfactant. One online definition of a surfactant reads: "a substance that tends to reduce the surface tension of a liquid in which it is dissolved". For the purposes of our discussion, we identify sodium lauryl sulfate as a detergent, rather than a soap. Detergents do not fail…