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- Chemistry is fun: Benzene Series (Part A)
Chemistry is fun: Benzene Series (Part A)
- Posted in Default
- By admin
- Date March 29th, 2012 11:31
The opposite of nature is impossible. ——Richard Buckminster Fuller
Hexagonal structures are often used in large modern buildings because their natural shape properties (strong, efficient and beautiful) are ideal for mechanical systems, structural support systems, sound and thermal insulation, and design elements.
Hexagonal shapes can be optimized to efficiently use material to create lightweight high strength materials. Hexagonal structures are increasingly used in modern buildings. The below images highlight a few real-life examples which use hexagonal forms in honeycomb or bionics structures. Trypophobia sufferers skip this pic. : )
Why are honeycomb cells hexagonal not square, round, triangular, rectangular, or even pentagonal? Hexagonal shapes are the most efficient shape for bees to live and store food. Geometric studies of honeycomb patterns reveal that no other shape can create more space per unit of material. Circles for instance leave space, and squares create smaller areas. Ask your engineering friends - they will confirm that hexagonal structures provide the most efficient strength which is why hexagons are used to support airplane wings and satellites walls.
The hexagonal masterpiece is also the basic structure of snowflakes. Hexagons form in a wide variety of intricate shapes to create each snowflake. This variation has of hexagonal structure is the root of the popular expression that "no two snowflakes are alike". Some snowflakes do not have equilateral sides. Uneven temperatures, dirt, and other environmental variables can create lopsided snowflakes. Many snowflakes are symmetrical and intricate. This is because a snowflake's shape reflects the internal order of water molecules. When in the solid state (ice or snow) molecules form weak bonds (called hydrogen bonds) with one another. These ordered arrangements result in the symmetrical, hexagonal shape of the snowflake. During the crystallization process, water molecules align themselves to maximize attractive forces and minimize repulsive forces. Consequently, water molecules arrange themselves in predetermined spaces and in a specific arrangement. Water molecules simply arrange themselves to fit the available spaces and maintain symmetry. The result is a hexagonal structure.
In organic compounds, the structure of benzene, the simplest aromatic hydrocarbon, is also hexagonal. Benzene ring structures have an interesting purpose.
A 19th century German chemist, August Kekulé, was grappling with a difficult problem. He was attempting to figure out the atomic structure of the molecule benzene (C6H6). Scientists knew which specific atoms were in benzene, but they had no idea how these atoms could possibly fit together to make the molecule itself . From what they could tell, benzene shouldn’t exist. Maybe because Kekulé is a typical Virgo Man (brainy mind, thinking, analyzing, sorting, organizing and doing all such things, which work towards making things right and perfect), one night he had a dream of a snake eating its own tail; when he awoke next morning he realized that this was the key to the benzene puzzle. The structure of the molecule was that of a ring and the Kekulé Structure was born.
Today, chemistry students typically use the Kekulé Structure because it is easy to understand how chemical reactions work. This representation does not accurately describe how benzene impacts human health. The single and double bonds shown in the Kekule Structure do not actually exist. The Skeletal Structure is a more accurate representation of what actually happens in nature. The incredible simplicity and stability of hexagons make it easy for benzene molecules to bond to other molecules. In this sense, hexagons are tragically beautiful - they easily bond to DNA molecules and cause genetic mutations.
What exactly is benzene? It's a colorless, flammable liquid with a sweet odor. It evaporates quickly when exposed to air, thus the main route of exposure (47-80%) is through inhalation. Benzene can also be absorbed through the skin when direct contact with a source, such as gasoline, is made.
Health hazards of benzene include leukemia, particularly acute myeloid leukemia (AML). Studies (Link to :http://www.cancer.org/Cancer/CancerCauses/OtherCarcinogens/ IntheWorkplace/benzene )conducted on workers who have been exposed to high levels of benzene (chemical companies, shoe factories, oil refineries) have revealed higher rates of leukemia among the patients studied.
Benzene appears on our Hazard Lists, including
Carcinogenicity: (P65) (IARC) (MAK) (NTP-CERHR)
Mutagenicity/Genotoxicity: (CLP) (R46)
Reproductive: Toxicity (P65)
Developmental: Toxicity (P65)
Systemic Toxicity / Organ Effects: (R48) (H372)
Irritation/Corrosivity (Skin/Eyes): (R36)
Acute Aquatic Toxicity: (H401) (H402)
P65 - Proposition 65. California EPA, Office of Environmental Health Hazard Assessment. http://www.oehha.org/prop65.html
IARC - International Agency for Research on Cancer (IARC), Agents Reviewed by the IARC Monographs http://monographs.iarc.fr/ENG/Classification/index.php
MAK - MAK Commission of Germany; Occupational Toxicants and MAK Values: Annual Thresholds and Classifications for the Workplace http://www.dfg.de/en/dfg_profile/statutory_bodies/senate/health_hazards/structure/working_groups/derivation_mak/index.html
NTP - US National Institutes of Health, National Institute of Environmental Health Sciences, National ToxicologyProgram (NTP), Report on Carcinogens (ROC) http://ehis.niehs.nih.gov/roc
DOT - US Department of Transportation Hazardous Materials Regulations http://environmentalchemistry.com/yogi/hazmat/placards
to be continued...