organic chemistry Archives

17Aug 2019 by Vincent Summers No Comments

Woodward cis-Hydroxylation Reaction

Silver acetate, in combination with iodine, forms the initial reactant package for the Woodward reaction. This reaction, carried to completion, selectively converts an alkene into a cis-diol. The prefix cis- refers to the addition of two atoms (or groups of atoms) to the same side of a molecular double bond. Trans-, when used, refers to addition across the double bond – of one atom or group to one side, one to the other side. The Mechanism The mechanism is illustrated in the image (below) up to the point of hydrolysis. The product of that hydrolysis is pictured in the introductory image. We see, first, the iodine splits, the I atom adding to the double bond. In the next part of the reaction, the silver atom attaches to the iodine, and…

13Apr 2019 by Vincent Summers No Comments

Organic Chemistry and Life: Has Vitalism Been Born Again?

Biology, Chemistry

[caption id="attachment_23607" align="alignright" width="480"] Pillars of Creation[/caption] The phrase ‘organic compound’ relates to the word organism, closely associated with life and life processes. Organic compounds largely consist of carbon atoms linked in chains or rings that contain hydrogen and frequently one or more other atoms called hetero atoms – notably oxygen, nitrogen, sulfur, and phosphorus. Inorganic compounds are everything else – for example, nickel chloride, ammonium nitrate, carbon dioxide, and phosphorus pentoxide. It is important to recognize that there are a relative handful of organic compounds that do not contain carbon chains or rings, but result from life processes, including for example, urea, NH2-CO-NH2.. During the 1800s, scientists widely believed organic compounds could not be generated in the laboratory. However, in the year 1828, chemist Friedrich Wöhler converted inorganic ammonium…

16Nov 2014 by Vincent Summers No Comments

Terpenes and Terpenoids: Isoprene Rule

Chemistry

There are thousands of chemical compounds in nature. They are divvied up into categories or classifications. These include hormones, alkaloids, vitamins, neurotransmitters, enzymes, proteins, and nucleic acids. One group of chemicals follows a structure rule called the isoprene rule. Many every day substances are part of this group. One example is turpentine. Another is beta-carotene (the source of the orange color in carrots). Chemicals such as these derived from isoprene are called terpenoids. Structure and Statement of the Isoprene Rule Isoprene consists of carbon and hydrogen. But it is not limited to single bonds. See the image of isoprene (C5H8) featured with this article. The double lines stand for double bonds. Since the carbon pairs involved have two bonds rather than one, a hydrogen atom is missing from each of them.…

22Aug 2014 by Vincent Summers No Comments

Explaining Saturation and Unsaturation

Chemistry

What is Saturation? What is Unsaturation? Even those scientifically uninclined use the words. Saturation, unsaturation, and polyunsaturation are dietary terms closely associated with health. Most know they are also chemical terms. But they don't understand what they mean. This is a shame, since "saturation" can be easily understood by any bright student. Saturated Hydrocarbon Linkage Living matter (plant or animal) is made of of organic compounds. These include (but are not limited to) fats, carbohydrates, and proteins. All these substances contain a kind of backbone or chain, of atoms of carbon (C) bonded to atoms of hydrogen (H). Each carbon is capable of bonding with four hydrogens. [sc name="MidArticleAdsense"] For purposes of illustration, we'll assume we have before us a chain of four carbon atoms, with every available bond possibility…

21Aug 2014 by Vincent Summers No Comments

Cubane: The Chemist’s Toy?

Chemistry

Cubane is an organic hydrocarbon. It consists of carbon and hydrogen and is cubic in shape. It is a very curious substance, indeed. With no practical purpose in view, it was first prepared in 1964. There is an endless number of theoretical molecular possibilities in the world of organic chemistry. Some chemicals are simple. Others are complex. Some are of practical use to mankind. Some are mere toys of the intellect. Yes, adults must have their toys! Cubism "We do the difficult immediately. The impossible takes a little time." Chemists enjoy challenges. One challenge was to synthesize cubane (C8H8). It is a cut with a carbon atom at each corner. Attached to each of them is one hydrogen atom (see the image). Now carbon "prefers" to form angles of 109.5…

20Jan 2014 by Vincent Summers 1 Comment

Organic Chemistry: Pushing Electrons

Chemistry

Scientists desire to solve complex problems with exact precision, but sometimes it just is not practical. Simplifying is necessary. For the organic chemist, one form of simplifying is the idea of pushing electrons. To illustrate, high school physics instructors introduce the concept of massless strings and frictionless pulleys. No such things exist. Still, this fiction enables the beginning student to isolate what is important. Spark Notes informs us that college entrance examinations generally employ such contrivances. Constructs, Artifices, Contrivances Physicists are not the only ones to employ constructs and contrivances to simplify problems and arrive at an answer. The organic chemist must understand very complex compounds and the reactions leading to their formation. One of the best known contrivances is that of pushing electrons or pushing arrows. The great thing…

20Oct 2013 by Vincent Summers No Comments

Chemicals With the Same Empirical Formula

Chemistry

An empirical formula lists the elements of a compound but not the structure. Oxalic acid has the formula C2H2O4. Its structure is HOOC–COOH. Multiple compounds can have the same empirical formula and a different structure. The Same Yet Different Location of a specific kind of bond may make the difference. There are compounds with the same empirical formula in which spatial orientation is the only difference. Sometimes one structure can be changed into another structure of the same formula. Most often compounds having the same formula but different structures are completely unrelated. Simple Bond Shift In some cases, a simple bond shift produces different structures with no formula change. An example is 1-butene and 2-butene. The first has the structure H2C=CH-CH2-CH3. The second has the structure H3C-CH=CH-CH3. Both have the…

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…