Chemistry Archives - Page 13 of 22

31Aug 2016 by Vincent Summers No Comments

Corncob Destructive Distillation: Hemicellulose to Xylose to Furfural

What does corncob destructive distillation produce? A most interesting product—furfural. What is it? What is it good for? What is Furfural? Furfural is an interesting organic compound, possessing a five member ring structure with a heterocyclic atom (oxygen) and several functional groups built in. It is an ether, a diene, and an aldehyde. What is the Reaction? Corncobs1 are rich in hemicellulose. Hemicellulose can be broken down to produce the five-carbon sugar—xylose, C5H10O5. Xylose can react further to produce the heterocyclic aldehyde furfural, IUPAC2 name furan-2-carbaldehyde. Corncobs (hemicellulose) → C5H10O5 → furfural (see diagram) The steps can be combined. The resultant reaction process is termed destructive distillation. Corncob Destructive Distillation The corncobs may be dried and chopped into tiny bits the size of a grain of corn or smaller. These…

06Aug 2016 by Vincent Summers 1 Comment

Make Homemade Iron Gall Ink from Oak Tree Galls

Chemistry, Education

[caption id="attachment_15237" align="alignright" width="480"] Oak tree gall.[/caption] As you guide your shopping cart down an aisle not devoted to foodstuffs, you spot a bag of a dozen pens on sale for an acceptable price. You grab a pack and move on… At one time, you might have had to prepare homemade iron gall ink from oak tree galls. Oak Tree Galls What are oak tree galls? These generally round growths are produced by the interaction of plant hormones of an oak tree, combined with growth regulating chemicals produced by gall wasps and other insects or mites. The galls are lightweight and filled with air and fibers. They are rich in gallotannic acid, which is broken down by water into tannic acid, one of the ingredients used to make ink. History…

16Jul 2016 by Vincent Summers 3 Comments

The Bent Water Molecule – Why Is It Bent?

Chemistry, Physics

[caption id="attachment_14934" align="alignright" width="480"] Liquid Water (Left) - Ice (Right)[/caption] The water molecule, H₂O, consists of two hydrogen atoms and one oxygen atom. A naïve attempt at writing its structure out in full is H‒O‒H. What’s naïve about this? This drawing is linear—a straight line. It is naïve because the water molecule is a bent water molecule... bent at about 104.5°. It is a good thing for us that this is so, since this imparts a degree of polarity to the water molecule. Polarity, in turn, gives rise to hydrogen bonding. The hydrogen bonding of molecules assures water’s liquidity. In addition hydrogen bonding influences water’s crystallization, so that ice is lighter than very cold water. Ice thus floats, forming an insulating blanket atop lakes and other bodies of water. This…

13Jul 2016 by Vincent Summers 2 Comments

Cooked Blueberries Taste Different – Why?

Chemistry, Food

Moderate heating of most single chemical compounds simply raises their temperature. Perhaps there may be an accompanying change of state. Thus ice if heated forms liquid water. But with increased heat, compounds can be made to break down. For instance, sugar melts and caramelizes. Biological systems, such as fruits, may experience cell wall breakdown and a number of chemical changes. Consider one example: cooked blueberries taste different from raw blueberries. Why is that? Relevant Blueberry Chemistry Much of the blueberry chemistry relevant to our discussion stems from compounds containing the same skeletal structure, that of the molecule flavone. Flavone has two rings: one large, one small. The larger ring includes an ether linkage (–C–O–C–) and a ketone group (–C–(C=O)–C–). The compounds as a group are the flavonoids. [caption id="attachment_19735" align="alignleft"…

06Jul 2016 by Vincent Summers 2 Comments

The Molecular Structure of Hydronium Ion Hydrate

Chemistry, Physics

[caption id="attachment_16126" align="alignright" width="440"] Simple hydronium ion, unhydrated.[/caption] Abstract: The water molecule, H2O, can attach a hydrogen ion (H+) perhaps from a dissolved acid, to become a hydronium ion, H3O+, sometimes called a hydroxonium ion. This ion, if surrounded by water molecules, can form additional hydrogen bonds with them as well. The question is what is the molecular structure of the resulting hydronium ion hydrate? The mind conceives two serious possibilities. But what do studies reveal? Background It is a general principle of nature that a system is more stable if charges are spread out as much as possible. In the field of chemistry, the best known example of this involves water. Although the sum total of the electric charge of a neutral water molecule is zero, as the image…

04Jul 2016 by Vincent Summers 2 Comments

Heavy Water –vs.– Regular Water

Chemistry, Physics

[caption id="attachment_14687" align="alignright" width="440"] Heavy Water & Water - Image by Author.[/caption] Hydrogen exists as three varieties or isotopes: protium, deuterium, and tritium. Heavy water, or deuterium oxide (D₂O) is the same compound as ordinary or tap water (H₂O) with one structure difference. Most of the hydrogen atoms in tap water have zero neutrons in their centers, or nuclei. On the other hand, every atom of deuterium contains precisely one neutron. We will not discuss tritium, with its one proton and two neutrons. [caption id="attachment_14693" align="alignright" width="400"] Protium & Deuterium Hydrogen - NASA[/caption] A Closer Inspection of Hydrogen Isotopes The mass of an atom is determined by the nucleus. Since the weight of a proton and that of a neutron are nearly identical, deuterium atoms have a mass essentially double…

24May 2016 by Vincent Summers No Comments

Why Cyclodecapentaene is Not an Aromatic Hydrocarbon

Chemistry

[caption id="attachment_16073" align="alignright" width="440"] Fig 1. Cyclodecapentaene - all cis form.[/caption] There are aromatic hydrocarbons and there are non-aromatic hydrocarbons. For basic mono-ring structures that have alternating carbon-carbon double bonds, there is a rule called Hückel’s rule that defines whether a given hydrocarbon can be aromatic or not. It might seem, at first that cyclodecapentaene (C10H10 or [10]-annulene) should be aromatic. Yet, cyclodecapentaene is not an aromatic hydrocarbon. Let’s find out why not. A Few Simple Rules for Aromatic Behavior The double bonds in the ring must be conjugated (alternating). This allows for the electrons to be delocalized [in conceptualization be flipped in either a clockwise or counterclockwise direction]. This allows for the presence of what is called a ring current. The ring must be flat. The mono-ring must feature…

18May 2016 by Vincent Summers 6 Comments

Total Energy in One Hydrogen Atom

Chemistry, Physics

[caption id="attachment_14456" align="alignright" width="440"] Hydrogen Bomb[/caption] Hydrogen is the lightest of the elements. However, there are three isotopes of hydrogen. The lightest of these is protium. It contains just one proton and one electron. Let’s determine the total energy of one protium atom. Its mass is 1.007822 atomic mass units. So what is the total energy one hydrogen atom produces if obliterated? By obliterated, we mean 100% conversion from matter to energy, not the mere energy of separation of particles, as in fission. Einstein’s Mass-to-Energy Equation In our calculating, it is important we stick to proper units. If we were cooking and the recipe called for a cup of flour, would we substitute a tablespoon? Our equation is Einstein’s mass to energy expression, E = mc² If the mass is…

16May 2016 by Vincent Summers 1 Comment

Azulene or Cycloheptatrienyl Cation Cyclopentadienyl Anion “Salt”?

Chemistry, Education

[caption id="attachment_14421" align="alignright" width="440"] The dipolar azulene hydrocarbon[/caption] Azulene is a fascinating hydrocarbon. It is bicyclic, meaning it has a kind of double ring structure. It is a seven-member ring adjoined to a five-member ring by a shared two-carbon wall. One ring resembles cycloheptatriene. The other ring, cyclopentadiene. And yet, there is something different about azulene. Or should we say some things different? Unusual Qualities Although azulene is a hydrocarbon, it is a deep blue hydrocarbon, something very much out of the ordinary. The Lactarius indigo mushroom, in fact, gets its blue coloration from a derivative of azulene. In addition, although most plain hydrocarbons have little or no dipole moment, azulene has a dipole moment of 1.08 Debye units. This is equal to that of the nitrogen-containing diphenylamine molecule. [caption…

16May 2016 by Vincent Summers No Comments

Cyclobutadiene Antiaromatic or Other Destabilization Factors?

Chemistry

Clearly cyclobutadiene is not aromatic. Is cyclobutadiene antiaromatic? Or is its lack of stability due to other factors? Cyclobutadiene is a four-carbon hydrocarbon. The –diene part of its name indicates it has two double bonds. The cyclo– part indicates it is not a chain structure, but a cyclic (ring) structure. Now double bonds hold atoms tighter than single ones do. So they are shorter than single bonds. This causes cyclobutadiene to assume a rectangular shape. If it were square instead, it would indicate the four carbon to carbon bonds were identical, and aromatic. Cyclobutadiene's four hydrogen atoms point away from the ring. Analyzing the Structure Cyclobutadiene is flat. The two double bonds of cyclobutadiene are conjugated. That is, their ring structure alternates double bond, single bond, double bond, single bond.…