Chemistry Archives - Page 4 of 22

10May 2019 by Vincent Summers No Comments

Motor Oil Degradation in Automotive Engines

Why is it so important to change the motor oil in your car? The answer is due to motor oil degradation. Unrecycled motor oils originate from naturally occurring crude oil. As such, motor oils are necessarily a complex combination of organic compounds: Molecules made simply of carbon and hydrogen. A percentage of these hydrocarbons include ring structures—whether saturated aliphatic rings or aromatic rings (benzene or polycyclic). However, the largest percentage of motor engine oil consists of straight and branched chain hydrocarbons of varying lengths. Motor oils are high-quality lubricants, but even the best of these products will degrade with use. Why is Oil a Lubricant? A good lubricant must readily flow and have sufficient viscosity. It should not freeze in even cold environments. It should possess a high level of…

10May 2019 by Vincent Summers No Comments

Sulfur Analogs of Oxygen-Containing Organic Compounds

Chemistry

[caption id="attachment_24653" align="alignright" width="480"] Common oxygen-containing organic compounds[/caption] Organic compounds contain carbon and hydrogen, and occasionally other elements. Most notably, these include nitrogen and sulfur, but also phosphorous, chlorine, bromine, and iodine. Simple oxygen-containing organics, including n-butyl alcohol, benzaldehyde, methyl ethyl ketone, diethyl ether, and tert-butyl peroxide appear in the illustration at top. An analog is a structure which is similar to another structure, except that one atom or group is replaced by another (similar-behaving) atom or group. Here, we will discuss sulfur analogs. Alcohols The generic structure for a simple hydrocarbon, a compound of hydrogen and carbon, is usually written RH. The equivalent for an aromatic structure is ArH. An alcohol has one hydrogen atom replaced by an –OH group. Hence, an alcohol is written generically, R–OH. The aromatic…

10May 2019 by Vincent Summers No Comments

Electronegativity of Atoms: What are Determining Factors

Chemistry, Physics

[caption id="attachment_24637" align="alignright" width="480"] 5d molecular orbital - Image Dhatfield[/caption] When two different types of atom are bonded together, they do not share their bond electrons equally. This is because each type of atom possesses its own charge environment, which results in an atom’s electronegativity. Electronegativity is the measure of an atom’s ability to attract additional electron density to itself. For example, Sodium seeks to give an electron to become a positive ion, Na+. It has a very low electronegativity. Iodine wants to gain an electron to become a negative ion, I-. It has a relatively high electronegativity. Charge Environment Atoms vary in electronegativity, and bonds vary according to constituent atom electronegativities. The electronegativity of an atom depends upon its charge environment. That environment depends primarily on three things... Distance…

05May 2019 by Vincent Summers 1 Comment

From Acids to Superacids: From Lavoisier to Olah

Chemistry, History

Acid theory evolved in stages. Our understanding of what constitutes an acid has improved, but that is not all. As a result of our better understanding, acids of greatly increased strength – superacids – have become available, as well. Early Acid Theory – Lavoisier [caption id="attachment_24574" align="alignleft" width="240"] Lavoisier & wife[/caption] The 18th century French chemist, Antoine Laurent Lavoisier, later guillotined by French revolutionaries, developed a theory of acids inaccurately based on a required presence of oxygen. This theory lasted into the 19th century. Its popular downfall was prompted by its undue restrictions on what constitutes an acid. Many acids contain no oxygen whatsoever. Hydrogen and Acids – Baron Justus von Liebig [caption id="attachment_24577" align="alignright" width="240"] Leibig[/caption] Although there was no detailed theory, credit should be given to Justus von…

02May 2019 by Vincent Summers 2 Comments

Differences Between Bound and Unbound Electrons

Chemistry, Physics

Atoms are constructed of a central nucleus, containing positively-charged protons and uncharged neutrons, plus orbiting, negatively-charged electrons, in number equal to the number of protons. Although an electron carries a charge equivalent (though of opposite polarity) to that of a proton, its mass is a mere 1/1836th that of a proton. Some mistakenly think the electron isn’t a particle at all, but a cloud. This inaccurate notion doubtless arises from the cloud-like appearance of the probability distribution curve of an electron in its orbit. At any rate, an electron generally exhibits particle-like properties, and is best mentally envisioned as a particle. How the particle we call an electron behaves depends upon the condition in which we find it. There are important differences between bound and unbound electrons. The Free-Moving, Unbound…

25Apr 2019 by Vincent Summers No Comments

Gutta Percha: From Underwater Cables to Golf Balls to Dental Work

Chemistry, History

[caption id="attachment_24465" align="alignright" width="340"] From the 1851 book: Gutta Percha, Its Discovery, History, and Manifold Uses[/caption] Gutta percha thermoplastic1 is a tough and leathery resinous produced from the milky fluid tapped from certain trees. Isoprene is an extremely important building block widespread in nature. The main component of gutta percha is, in fact, the trans-1,4-isomer of polyisoprene. The cis-1,4,-isomer is, interestingly enough, the primary constituent of natural rubber. It is produced from the milky fluid tapped from "other" trees. The reason for the considerable difference in physical characteristics between rubber and gutta percha (or, rather the trans and cis isomers of polypropylene) is the greater crystalline character of the trans isomer. Notice the difference between the trans and cis isomers in Image 2. How do these isomers differ? Synthesis from…

24Apr 2019 by Vincent Summers No Comments

Limonene Citrus Cleaner Chemistry

Chemistry

[caption id="attachment_24444" align="alignright" width="480"] A juicy wedge o' lemon.[/caption] Citrus fruits offer both pronounced flavor and pungent aroma. Where does the pungency come from? From the terpene limonene – more specifically, the dextrorotatory enantiomer¹, d-limonene. Although modern terminology is switching from (D)extro and L(evo) notation to S(inister) and R(ectus), we’ve chosen the older terminology, more often associated with limonene. What is Limonene? Limonene is useful commercially in environmentally-safe cleaning formulations, as a solvent, and as raw material in the synthesis of other chemicals, such as carvone. This chemical is also useful as an insecticide and for assorted other purposes. Manufacturers separate limonene from the fruit’s peel by means of steam distillation, or a centrifugal process. Lab Synthesis of Limonene Citrus Cleaner from Isoprene Labs can prepare limonene (a mixture of…

24Apr 2019 by Vincent Summers 2 Comments

Chemical Separation by Fractional Distillation and Crystallization

Chemistry

[caption id="attachment_24415" align="alignright" width="480"] Distillation apparatus[/caption] Solids may be subdivided into amorphous solids and crystalline solids. Amorphous solids possess limited order in the way molecules are bonded to each other. Crystalline solids, on the other hand, exhibit an exceptional degree of order. Logic should tell us a mixture of crystalline solids should be capable of chemical separation and purification through some reiterative crystallization process, based on relative solubilities. This proves to be true. The process is called fractional crystallization. Before discussing fractional crystallization, it might prove wise to discuss the simpler process of fractional distillation, the separating by distilling of a mixture of liquids possessing markedly different boiling points. Ordinary Distillation Consider an example of two liquids, Component A and Component B, that are miscible (they dissolve completely one within…

23Apr 2019 by Vincent Summers No Comments

Prussian Blue – The Traditional Blue of Blueprints: Its Chemistry?

Chemistry, History

[caption id="attachment_24391" align="alignright" width="480"] A Canadian architectural blueprint. Image by Chris Gonzaga.[/caption] The image you see at right is a traditional architectural blueprint. In fact, this style of blue-inked drawing is how the word blueprint originated. Now the chemistry of this blue colored “ink” is of interest, both historically, and from the science perspective. Let’s see how. Identifying the Blueprint Ink The blue ink has a number of names including Paris Blue and Berlin Blue. But the name it is best known by historically is Prussian Blue. Perhaps you will note Prussian Blue is similar to another name, Prussic Acid. Prussic Acid is another name for the deadly poisonous hydrogen cyanide, HCN. And in fact, the ink is closely connected to this acid. But which was first to be called…

23Apr 2019 by Vincent Summers No Comments

Diatomic Molecules: Degrees of Freedom and Equipartition of Energy

Chemistry, Physics

[caption id="attachment_24378" align="alignright" width="480"] A useful, but rough working model[/caption] Diatomic molecules have three translational degrees of freedom – but they have rotational and vibrational varieties as well. How do all these degrees of freedom relate to the distribution of molecular energy? To Begin With The location of any particle lies within three-dimensional space. The direction in which a particle moves is described by the three variables, usually written X, Y, and Z. As Ken Koehler of the University of Cincinnati informs us, atoms may be viewed as single points without size – so there are only three translational degrees of freedom for a given atom. Degree of Freedom of Diatomic Molecules Although it’s tempting to assume only three degrees of freedom exist for all “particles,” such is not the…