Chemistry Archives - Page 16 of 22

07Dec 2015 by Vincent Summers No Comments

Guar Gum – Uses, Contraindications, and Diversity

Through past decades, food products have been formulated and reformulated. This has been done so as to achieve good quality at lower cost. One of the ways to reduce cost is to replace high price thickeners with cheap substitutes. These include seaweed extracts and vegetable gums. Among them are carageenan, locust bean, xanthan and guar gums. What exactly is guar gum? From Beans to Endosperm Guar beans are harvested from the guar gum bush. It is grown in India and Pakistan. In the U.S., it is found in Texas. Gums are used to impart creaminess. They are thus added to dairy products. They also are used in place of ingredients that contain gluten. The best known food in which this has occurred is certain breads. The endosperm is the desired…

13Nov 2015 by Vincent Summers No Comments

Aluminum Was a Precious Metal

Chemistry, Technology

[caption id="attachment_10187" align="alignright" width="440"] Bas-relief aluminum door in the Hunt Library.[/caption] Various materials and artifacts bring a high price. This is because of their beauty, low availability, or craftsmanship. Some desirable objects are so rare we consider them precious. These include platinum, silver, and gold. But not aluminum. Yet during the 19th Century this bright and shiny metal was highly valued. How can that be so? Aluminum Deposits It is the most common metal in earth. It is not especially beautiful. So why did the metal once bring so high a price? In a sense it was scarce. It was unavailable. Availability [caption id="attachment_20663" align="alignright" width="200"] 1893 cast aluminum angel statue, Piccadilly Circus, London - Image by Michael Reeve[/caption] Diamonds are highly prized. Yet, they are fairly common. The number…

11Nov 2015 by Vincent Summers 1 Comment

Lactones: What are They? How Are They Made?

Chemistry

The simplest lactones are unsubstituted cyclic esters that can conceivably be prepared from single linear molecules that contain both the alcohol and carboxylic acid functionalities. Notice the featured image of this article. It pictures four of the simplest lactones. The single molecule preparations from linear structures should be: HO-CH₂-COOH → α-acetolactone + H₂O HO-CH₂-CH₂-COOH → β-propiolactone + H₂O HO-CH₂-CH₂-CH₂-COOH → γ-butyrolactone + H₂O HO-CH₂-CH₂-CH₂-CH₂-COOH → δ-valerolactone + H₂O α-acetolactone Known more simply as acetolactone, this molecule is unstable and hence transient. The synthetic reaction for acetolactone written above, would produce close to 100 percent of the desired product, if it were stable. β-propiolactone [caption id="attachment_10179" align="alignright" width="308"] Preparation from carbon monoxide and ethylene oxide.[/caption] Sometimes called simply propiolactone, this molecule is stable, but is being phased out for many applications,…

19Oct 2015 by Vincent Summers 2 Comments

Lotus Effect: Vibrations and Superhydrophobic Behavior

Biology, Chemistry, Physics

[caption id="attachment_9623" align="alignright" width="480"] The lotus leaf is superhydrophobic and self-cleaning.[/caption] Superhydrophobic? What's that? A word in the Mary Poppins musical? There is much interest in a behavior of the lotus plant. It is the ability to shed water completely and take surface detritus along with it. This superhydrophobic property had been observed in nature. But at first it could not duplicated in the lab. In that setting, the leaves were wet. Superhydrophobic: But Not In the Lab? After some time, it was found even wetted leaves would produce the effect in the presence of vibrations, such as those from a stereo speaker. This was evidence energy, usually vibratory energy, was required. It lifts water out of the spaces between the cone-like waxy protrusions found on the surface. This property…

16Oct 2015 by Vincent Summers 1 Comment

How I Became the NRAO Electroplater / Electroformer

Astronomy, Chemistry

[caption id="attachment_9605" align="alignright" width="480"] NRAO Green Bank Telescope.[/caption] Little did I know my future lay with the NRAO. As early as the 8th grade, my teacher informed us we needed to choose a career. I chose astronomy. My mother informed me, “No. There is no future in astronomy.” I was downhearted! Her friend’s husband worked for Union Carbide. I asked Mom if chemistry was acceptable? She said that was fine. Curiously, in high school I became a close friend of a kid from Canada who loved chemistry, Charles Harris. I greatly admired him. He was instrumental in my growing appreciation of chemistry. From College to Employment Beginning in my junior and senior years at high school, and later at college, I found myself drawn to organic chemistry and to quantum…

25Sep 2015 by Vincent Summers No Comments

Oil and Water Do Not Mix – Why?

Chemistry

[caption id="attachment_8586" align="alignright" width="440"] Oil and water just plain do not mix.[/caption] Oil and water do not mix! Some liquids are miscible; that is, they mix completely. Other liquids do not permanently mix. They are immiscible. The best known example of this is oil and water. “Putting those two together is like mixing oil and water.” This means that for practical purposes, the two don’t get along at all. Why Don’t They Mix? Oil and water don’t mix for a basic physical reason curiously easy to explain by comparison with a magnet. Consider first the formula, and then the structure, of water and we’ll see how this is so. The Formula of Water Water is most commonly written H₂O. Two hydrogen atoms (H) are combined with one oxygen atom (O).…

11Sep 2015 by Vincent Summers No Comments

Do Double Bonds Flip? Does Electron Density Move?

Chemistry

[caption id="attachment_7788" align="alignright" width="440"] 1,3,5 Hexatriene - NIST Image[/caption] How do double bonds flip, and what is the significance? The shorthand drawing of a double bond looks like an equal sign between two atoms. The double bond between the two carbon atoms of ethene gas, H₂C=CH₂, well illustrates this. Some organic compounds possess conjugated (alternating) double bonds. A simple example of this is 1,3,5-hexatriene. [caption id="attachment_7785" align="alignright" width="340"] Fig. 1. 1,3,5 Cyclohexatriene.[/caption] What If? But what if the ends of that 1,3,5 hexatriene are joined, with the loss of two hydrogen atoms, to make a ring one might be tempted to call 1,3,5-cyclohexatriene? In fact, such a molecule, if flipped left-to-right, is seen to be identical with 2,4,6-cyclohexatriene! The numbers can be dropped and the molecule can simply be named…

02Sep 2015 by Vincent Summers 1 Comment

Important Differences between Lime and Limestone

Chemistry

[caption id="attachment_7743" align="alignright" width="480"] Lime stripes on football field.[/caption] I feel certain everyone has heard, whether in the realm of gardening or in the realm of sports, the words lime and limestone. Perhaps without even consciously thinking of it, these two words have been considered by many to be synonymous. Yet they are by no means synonymous. Lime Lime is used in delineating the zones and yard lines of a football field. Lime is a fine white powder. It is occasionally spread thinly over lawns as well. What is lime chemically speaking? It is calcium oxide, chemical formula CaO. By slaking lime with water, one obtains, naturally, slaked lime! Slaked lime has the chemical formula Ca(OH)2. The slaking of lime is written, in shorthand, CaO + H2O → Ca(OH)2 +…

17Aug 2015 by Vincent Summers 2 Comments

The Dipolar Molecule Water – Mickey the Dipole

Chemistry

[caption id="attachment_16242" align="alignright" width="440"] The bent water molecule manifests uneven charge distribution. Image by Qwerter CC-by-SA 3.0.[/caption] Mickey the Dipole? Everyone knows H₂O is the chemical formula for water. H stands for hydrogen. O stands for oxygen. The water molecule is made from two atoms of hydrogen and one atom of oxygen. Hydrogen atoms have one proton and one electron. Ordinary oxygen atoms have eight protons and eight neutrons and eight electrons. For the purposes of this discussion, we can forget the protons and the neutrons. Oxygen has a thirst for electrons. Hydrogen is "happy" to give up its electron. The reaction of hydrogen with oxygen (each of which exist as a pair) is, 2 H2 + O2 → 2 H2O The hydrogen parts are positive (H⁺). The oxygen part…

12Aug 2015 by Vincent Summers 1 Comment

Are Additional Varieties of Aromaticity Achievable?

Chemistry

[caption id="attachment_7679" align="alignright" width="380"] A stick model of the aromatic molecule, benzene.[/caption] I am a retired chemist. I have no laboratory, and I have no close affiliations, but I do retain a brain. One of my favorite topics is aromaticity. Organic chemistry, essentially the study of carbon chemistry, features aliphatic compounds and aromatic compounds. Aromatic compounds, even being constructed from alternating (conjugated) double bonds, possess resistance against undergoing addition reactions, tending toward substitution reactions instead. An Idea Begins to Take Shape Realizing this, I began to wonder about a kind of aromaticity that might utilize triple bonds, rather than double bonds. However carbon-carbon triple bonds force other atoms to take positions along the same axis as the triple bond. A ring created from alternating single and triple carbon-carbon bonds would…