Notes Organic Chemistry & AlkanesHistory:Vital Force Theory: organic molecules can only be created by living organisms.In 1828, Professor Wöhler was finishing up his post-doctoral work as a student. While working the laboratory he succeeded in synthesizing an organic compound, urea, previously observed only in living tissue. Wöhler, pictured below, made this organic compound from a non-living chemical substance, Ammonium Cyanate. He evaporated a solution of Ammonium Cyanate to produce Urea. Organic Chemistry has undergone a substantial change since then. There are well over a million synthetic organic compounds. Organic Chemistry is defined as the Chemistry of Carbon and its compounds.Carbon is a Lego like element.I use the analogy Lego’s because these atoms tend to form bonds with themselves creating different shapes. Like the two below, octane on the left and a steroid precursor on the right. The shapes are created by the chemical property of carbon to form 4 bonds.Hybridization:The 4 bonds carbon forms is explained by Linus Pauling’s theory of hybridization. Carbon atoms have an electron configuration of 1s2 2s2 2p2 This configuration corresponds to the following energy level diagram.2p2s1sFrom the looks of this diagram, carbon might form 3 bonds as appears to be nowhere for a 4th bond to form. Linus theorized that the two sublevels, s and p, in the second energy level formeda hybrid sublevel.This new energy level diagram is draw belowThis shows four open orbitals, allowing for the formation of four bonds. Linus won a noble prize for this theory. When carbon atoms are bonded using all single bonds the below shape forms from the combination of one s orbital and three p orbitals. This hybridization is named sp3. These shapes are verified by an analysis technique named X-Ray Crystallography. The compound is frozen then photographed with X-Rays. The resulting pictures have show this tetrahedral shape. In this instance the carbon atom forms bonds with 4 different objects, resulting in a tetrahedral shape, is shown above picture. This shape is formed by the repulsion of the electrons which surround all atoms. So, if four objects are connected to a central object the farthest these objects can be from each other forms a tetrahedral shape. The angle between these bonds is 109.5. The blue balloon looking objects represent the orbitals where the four electrons in carbons second energy level reside. This is the hybridization. Each of the four electrons have equal energy and are all in the same orbitals, they have been moved to the same “Shell” insteadof having the 2s electrons located inside or underneath the 2p electrons. This tetrahedral shape has also been verified by calculus. The addition of one sphere and threedumbbell shapes produces this tetrahedral shape.General Properties of Organic Molecules:1. Flammable2. High Vapor Pressure3. Odorous4. Covalently Bonded5. Non-Polar – functional groups can change these from non-polar to polar or cause the molecule to be bi-polar.6. Low Solubility in Water – due to being non-polar as water is polar7. Rate of Chemical Reaction is Normally Slow8. Normally Found as Gasses and Liquids at Room Temp9. Non-Conductive of Electrical CurrentAlkanes:The first classification for organic molecules is the most simple, the alkanet. The most simple alkanet consists of only carbon and hydrogen atoms connected by single bonds.Alkanes are common and for the most part chemically uncreative, the chemical reaction combustion being the major exception.Alkanes can be found in many common substances; natural gas, gasoline, plastics…The chemical formula can be generalized as:CnH2n+2Where n represents the number of carbons and 2n+2 equals the number of hydrogen’s. Nomenclature:Nomenclature is the scientific term for naming compounds. The governing body is “The International Union of Pure and Applied Chemistry”, or IUPAC for short. The following statement is from their web site:“The International Union of Pure and Applied Chemistry (IUPAC) serves to advance the worldwide aspects of the chemical sciences and to contribute to the application of chemistry in the service of Mankind. As a scientific, international, non-governmental and objective body, IUPAC can address many global issues involving the chemical sciences.”IUPAC was formed in 1919 by chemists from industry and academia. One of there main functions is to objectively create rules for naming compounds in the most simplified manner possible. This is equivalent to creating a new language, just like English grammar, there are rules.Even with the advent and acceptance of the IUPAC system some common names still persist, when discussing a substance the IUPAC name should be used but the common name will be accepted by most chemical organizations.Alkane Nomenclature:Naming of organic structures, unlike biological classification, follows a rigid set of rules. The International Union of Pure and Applied Chemistry, abbreviated IUPAC, came up with a set of rules that follows the same standards worldwide, and is accepted among all chemists. However,common names of compounds, or names that have historical roots, are still used today for manycompounds. The suffix for the alkane family is –ane.prefix – root – suffix prefix – where the substitutions are locatedroot – how many carbons are in the molecules longest chainsuffix – family – type of functional group (alkane, alkene, alcohol, ester, etc...) Root words are named for its number of carbons:# of carbons root1 meth-2 eth-3 prop-4 but-5 pent-6 hex-7 hept-8 oct-9 non-10 dec-Example:an alkane with 3 carbons is named propaneprop – for the 3 carbonsane – for the family alkane (meaning all single bonds) Formula Types:A variety of methods are used to describe a chemical compounds composition. Sometimes you will find a the chemical formula sufficient. Other times you need to see the structure drawn out, this is referred to as the structural formula. This is a larger drawing which will show the atoms are connected. Another is the condensed structural formula, this shows the connections in around about manner. Lastly, a more lazy form is the line structure. This simplified drawing assumes you know that carbon atoms make 4 bonds and that if you do not see a bond drawn assume a hydrogen is occupying the undesignated bond. Also all ends and turns in the line signify carbon atoms.Examples:Chemical
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