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Organic Chemistry 101 1 Carbon Bonding • Organic Chemistry – Branch of chemistry dealing with hydrocarbons and their derivatives. • Carbon Chain – Carbon atoms chemically linked to one another, forming a string-like molecular sequence. 2 Hydrocarbons • The carbon chain forms a “backbone” to which many other atoms and/or functional groups can be added. • Carbon’s ability to form multiple bonds is responsible for the tremendous number of organic compounds. 3 Terms to Know • Alkanes – hydrocarbons containing only single covalent bonds. • Saturated Hydrocarbons – Hydrocarbons consisting of molecules in which each carbon atom is bonded to four other atoms. 4 5 More Alkane Terms • Straight-chain alkane – Alkane consisting of molecules in which each carbon atom is linked to no more than two other C atoms. • Branched-chain alkane – Alkane in which at least one carbon atom is bonded to three or four other carbon atoms. 6 • Isomers – Compounds with the same molecular formula, but different structural formulas. • Not to be confused with isotopes. 7 8 Guidelines for naming branched chained alkanes • 1. Locate the longest continuous carbon chain. This designates the parent chain and the root word of the molecule. • 2. Number the parent chain such that the branch (substituent) falls on the lowest carbon number. • 3. Count the number of carbons in the branched chain. Use the same set of root words EXCEPT add the suffix –yl. 9 • 4. Designate the location of the branched group by placing the number followed by a hyphen before the name of the branched group. The name of the branched chain serves as the prefix of the parent chain. • 5. If there are more than one substituent, designate the position of every group and alphabetize the substituents. • 6. If there is more than one of the same branch on a chain, designate the positions of the substituent and name the branch with the additional prefix indicating how many times it occurs. 10 Beyond Alkanes • Saturated hydrocarbon – hydrocarbon consisting of molecules in which each carbon is bonded to four other atoms. • Unsaturated compound – organic compound containing one or more double or triple bonds per molecule. 11 Alkenes • Alkene – hydrocarbon containing a double covalent bond. –Ethene, propene, butene, pentene, etc. –Because of their double bonds, alkenes are much more reactive than alkanes. 12 Naming of Alkenes & Alkynes • 1. Identify the longest carbon chain that contains the multiple bond. • 2. Number the carbons such that the double or triple bond falls on the lowest carbon number. • 3. The first carbon atom involved in the bond is followed by a hyphen and placed in front of the parent name. • 4. Name the branches as described in alkanes. Branches are prefixes in the name. 13 Alkynes • Alkyne – hydrocarbon containing a triple covalent bond. –Ethyne, propyne, butyne, pentyne, etc. 14 More Organic Molecules • In addition to straight-chain and branchedchain alkanes and alkenes, there are also ring structures. –Imagine taking a hydrogen off of each end of a hexane molecule and a new bond forming between the end carbons. 15 H H H H H H H C C C C Cyclohexane C C H H H H H H H H HH H H C C H C H H C H C H C H H H H H H H H H H H H H H 16 Cycloalkanes • Cyclohexane is one member of a much larger group of saturated hydrocarbons with ring structures called cycloalkanes. • This group includes cyclopropane (C3H6) all the way up to an infinite number of carbons in theory. 17 Cycloalkenes • If a double bond is present in a hydrocarbon ring it is considered to be a cycloalkene. • The naming process is simple for alkane and alkene rings: just add a cyclo- prefix to their name(s). 18 Aromatic Compounds • Aromatic compound – ringlike compounds such as benzene that can be represented as having alternating double and single bonds between carbon atoms. • These compounds were named so because the first of their kind discovered had pleasant odors. 19 Aromatic Compounds • These compounds are considered to be unsaturated. • The simplest aromatic compound is benzene (C6H6). • While the original structure proposed for benzene showed alternating double bonds, most now think all bonds are equal – 1.5 bonds? 20 Benzene • Most people now draw benzene with a circle in the center to illustrate a “delocalized” electron system with all six carbons sharing the extra electrons. 21 Organic Molecules With Oxygen • Functional Group(s) – atom or group of atoms that impart(s) characteristic properties to an organic compound. • In this section we will focus on functional groups that contain oxygen. 22 Organic Compounds • When discussing organic compounds, the functional group is usually the focus and we don’t really care much about the rest of the molecule. • We use the letter “R” the stand for the REST of the molecule. 23 Alcohols (& Phenols) • Alcohols and phenols are organic molecules that contain a hydroxyl group. • Hydroxyl Group – A hydrogen bonded to an oxygen that is covalently bonded to the rest of the molecule. • We abbreviate: R-OH 24 Alcohols (& Phenols) • Just as with naming other alkanes and alkenes, the location of the hydroxyl group is determined by numbering the molecule such that the hydroxyl group has the lowest number possible. 25 Alcohols (& Phenols) H H C O H OH H methanol (methyl alcohol) phenol 26 Ethers • Ethers are very similar to alcohols except, instead of an oxygen being bonded to a carbon on one side and a hydrogen on the other, an ether’s oxygen is single-bonded to a carbon on each side. 27 Ethers • Ethers are named by saying the name of the carbon group on each side followed by the word “ether”. • No numbering is necessary. • We abbreviate: R-O-R’ 28 Ethers H H H H C O C H C H H H methyl ethyl ether 29 Aldehydes • Aldehydes contain a carbonyl functional group whose carbon is attached to a hydrogen on one side and a carbon on the other side. • Carbonyl group – A carbon double-bonded to an oxygen is a carbonyl group. 30 Aldehydes • Aldehydes are named with an “-al” ending. • Numbering (for location) of the carbonyl group is not necessary in the name because it is always located at the end. 31 Aldehydes H O H C C H H ethanal (acetaldehyde) 32 Ketones • Ketones are compounds in which the carbon in the carbonyl group is bonded to two carbons. • Ketones are named with an “-one” ending. • The location of the carbonyl group in the molecule is identified with the lowest number possible. 33 Ketones H O H H C H C C H H 2-propanone (acetone or dimethyl ketone) 34 Carboxylic Acid • Carboxylic Acids are compounds in which the carbonyl group is bonded to a carbon on one side and a hydroxyl group on the other side. • Named with an “-oic acid” ending. • Carbonyl does not need to be numbered since it is at the end. 35 Carboxylic Acid H O H C C O H H ethanoic acid (acetic acid) 36 Esters • Esters contain a carbonyl group where the carbonyl carbon is attached to a carbon on one side an oxygen on the other; the oxygen is then connected to another carbon. • Similar to an ether, but has a carbonyl group between the oxygen and a carbon. 37 Esters • Esters are named with an “-oate” ending. • Again, the carbonyl group does not need to be numbered since we name the group found on each side of it. • Many esters have pleasant odors. 38 Esters H O H H C C O C H H methyl ethanoate (methyl acetate) H 39 Condensation Polymers • Condensation Polymers – Polymers formed by repeated condensation reactions of one or more monomers. • Condensation Reaction – Chemical combination of two organic molecules, accompanied by the loss of water or other small molecule. 40 Condensation Polymers • One very common condensation polymer is polyethylene terephthalate (PET). It has many uses: –Thin film for videotape –The textile Dacron® –More than 2 million kg are produced each year in the U.S. 41