Chemistry Archives - Page 21 of 22

27Sep 2013 by Vincent Summers 3 Comments

Three Hydrogen Isotopes: Protium, Deuterium, Tritium

Elements are the building blocks of a chemist’s world. The first and simplest element is hydrogen, H. It is a gas at room temperature. A molecule of hydrogen gas consists of two joined atoms. However, we will discuss the lone atoms, which exist in three varieties: protium, deuterium, and tritium. All hydrogen atoms have an atomic number of 1. This means the central core or nucleus of any of the three varieties of hydrogen contains just 1 proton. All hydrogen atoms have 1 electron in an orbital outside the nucleus. What makes the three varieties different? The nucleus of hydrogen can include in addition to the proton, zero, one, or two neutrons. Protium Hydrogen without any neutron is protium. Hydrogen with one neutron is deuterium. Hydrogen with two neutrons is…

25Sep 2013 by Vincent Summers 2 Comments

On the Nature of Azeotropes

Chemistry

[caption id="attachment_4850" align="alignright" width="440"] Russian Vodka Still[/caption] Definition: azeotropes are a specific mixture of compounds that boil together as if they were a single substance, at constant temperature. Individual Boiling Points In most instances, liquids boil as pure substances at a specific temperature. It is this property that allows boiling (as a physical property) to be used as a means of separation. For instance, an ester may be produced by reacting an organic acid and an alcohol. The resultant ester may usually be separated by boiling from excess alcohol or excess acid. Yet, Occasionally In some instances, however, as for example in the case of ethyl alcohol and water, there may be a mixture that distills over, instead of a pure substance. Thus a “mixture” of approximately 95.6% alcohol and…

13Sep 2013 by Vincent Summers 1 Comment

Novel Wastewater Treatment – Reducing Nitrogen and Phosphorus

Biology, Chemistry

[caption id="attachment_19184" align="alignright" width="480"] Wastewater Treatment Plant[/caption] The University of Kansas, in conjunction with the City of Lawrence, Kansas, has been investigating a fascinating approach to reducing nitrogen and phosphorus from wastewater. It’s a process, really, that occurs in nature, with a minimum of artificial intervention. Simply put: still water containing an abundance of “nutrients” tends to produce a proliferation of green algae. A Most Interesting Approach Why not take advantage of that fact? And so, they have. In their September 2013 Issue, Treatment Plant Operator (TPO) magazine included a well-written piece by author Doug Day that greatly intrigued me. Not long ago, I was employed as a Wastewater Operator, Level III at the local Nelson County, Virginia treatment plant. I am a retired chemist. I had rejected a career…

14Aug 2013 by Vincent Summers No Comments

Mineral Acids – Common Oxy Acid Terminology

Chemistry

As a youngster, I decided to become a chemist when I grew up. And that is how it turned out. To become acquainted with my chosen profession, I had to learn its naming systems or nomenclature. This included the naming of common mineral acids. So called mineral acids contain hydrogen, at least one additional element (often from the right hand side of the periodic table), and varying amounts of oxygen. Mineral Acids with No Oxygen If no oxygen is present, the acid name usually employs the prefix hydro– and the suffix –ic. Thus HCl is named hydrochloric acid.¹ HBr is hydrobromic acid. Some other examples include hydrogen sulfide (H₂S), hydrogen iodide (HI), and hydrogen telluride (H₂Te). A little confusion arises when the element has a valence greater than -2, as…

15Apr 2013 by Vincent Summers 2 Comments

Pyrophoricity: How Does It Work?

Chemistry, Physics

[caption id="attachment_3651" align="alignright" width="440"] Pyrophoric ferro-cerium striker[/caption] A substance exhibiting pyrophoricity (including certain metals) reacts quickly with oxygen, producing heat, and bursting into flames. Alkali metals are pyrophoric, but there are other pyrophoric metals as well, given the proper conditions. Otherwise, they are stable and may be put to a number of uses without fear of bursting into flame. The overall principle is a simple one: metals are electropositive. Oxygen is electronegative. Almost all metals will react with oxygen to some extent. As a metal oxidizes, the reaction releases a little heat energy. If the heat cannot dissipate, it builds up. This speeds further oxidation, increasing the heat yet more. The metal may burst into flames. Those “Other” Metals Some alkaline earth metals such as calcium, and a few other…

01Apr 2013 by Vincent Summers No Comments

The Hydrolysis of Acetonitrile or Methyl Cyanide

Chemistry

Hydrolysis of acetonitrile (the adding of water to its triple bond) is a useful synthetic procedure. Alkali metals such as sodium (Na) and potassium (K) attached to the cyanide group (carbon and nitrogen joined by three bonds, ‒C≡N or -CN for short) is deadly poisonous. One factor making it so poisonous is most inorganic cyanides ionize in water. Dissolving cyanides separates the cation (for example, Na⁺) from the cyanide ion, ‒CN⁻. When an organic group is attached to ‒CN, the group is not ionized, even if the organic is water soluble. In such a case, the compound is called a nitrile. Nitriles are generally much safer to handle.* What some might call methyl cyanide, CH₃CN, is more accurately acetonitrile. Why acetonitrile? Hydrolysis of the ‒CN group produces acetic acid. Hydrolysis…

20Mar 2013 by Vincent Summers No Comments

Straight Chain Alkanes: Predicting Properties

Chemistry

Straight chain alkanes are compounds with a non-branched backbone of carbon atoms. In addition, as many hydrogen atoms as possible are attached to each carbon atom. Straight chain alkanes are “saturated” hydrocarbons, which means they are completely filled up with hydrogen. See Figure 1 for examples of straight chain, branched chain, saturated, and unsaturated hydrocarbons. Methylene With the exceptions of methane and ethane, straight chain alkanes differ in the number of methylene groups (CH₂) each contains. Thus the first five hydrocarbons, methane, ethane, propane, butane, and pentane are written, CH₄ CH₃CH₃ CH₃CH₂CH₃ CH₃CH₂CH₂CH₃ CH₃CH₂CH₂CH₂CH₃ Another method of writing straight chain alkane chemical formulas for the butane and pentane structures above is, CH₃(CH₂)₂CH₃ CH₃(CH₂)₃CH₃ General Formula From this, we can formulate the rule for the formula of a straight chain alkane…

26Feb 2013 by Vincent Summers 1 Comment

On the Nature of the Chemical Bond

Chemistry

[caption id="attachment_3393" align="alignright" width="440"] Proline - Ball and Stick Model CCA 2.5 by Peter Murray-Rust.[/caption] Atoms combine to form molecules. Atom A approaches atom B and cohesively attaches to it. Molecule AB is held together by a chemical bond.¹ That bond is written A–B, or in the case of multiple bonds, A=B, A≡B, etc. Factors in Bond Formation The primary bonding agency is electrostatic force. This is the force between electrical charges. A positive charge is due to a lack of one or more electrons, producing cations. A negative charge is due to an excess of electrons, producing anions. One of the simplest examples is the formation from sodium (Na) and chlorine (Cl) of ordinary table salt, sodium chloride (NaCl).² We write, Na – e⁻ → Na⁺ Cl + e⁻…

07Feb 2013 by Vincent Summers No Comments

Decarboxylation of Carboxylic Acids Useful in Synthesis

Chemistry

For one reason or another, it may be desirable to remove a carboxylic acid group (–COOH) from a molecule. This process is called, logically, decarboxylation. It may be the carboxylic group was previously introduced to guide some of steps in a synthesis. What? A Simple Example Consider the simple hexagonal ring, aromatic compound benzene, C6H6. From the top and clockwise, let's number the carbon atoms, one through six. If we wish to attach a group synthetically to the ring, how do we determine the ring carbon to which it will attach? It's simple. They're all identical. Whichever carbon atom it does attach to becomes the number one carbon atom! But say we want to attach another group to the No. 2 carbon atom. Well, in this situation, the carbon atoms…

04Feb 2013 by Vincent Summers 2 Comments

Epoxide Ring Preparation by Oxidation of Alkenes

Chemistry

How many have purchased a 2-tube pack of epoxy at their local hardware or grocery store? It’s a routine item we use to repair a variety of objects. But what is it that makes epoxy glue so strong? Its name gives it away. Epoxy glues use epoxy compounds. Epoxides. What is an epoxide? It’s Simple? Yes An epoxide is a molecule with a tiny 3-member ring in its structure. One atom is oxygen. Two are carbon. The epoxy link is illustrated in Figure 1. R₁, R₂, R₃, and R₄ are pendant groups. How is such a 3-member ring created? Often by the oxidation of an alkene. The reader may appreciate an example.1 Propene Let's try the oxidation of propene, CH3CH=CH2.2 What would be a suitable oxidizing agent for the reaction?…