“Organic compounds and Nomenclature”

Root of the name l This depends on the number of carbon atoms in the longest unbroken chain. 1 carbon chain …. Meth- 2 carbon chain …. Eth- 3 carbon chain …. Prop- 4 carbon chain …. But- 5 carbon chain …. Pent-

The “default” l This is a hydrocarbon that contains only single bonds. It has the suffix (ending) – ane Example A three carbon chain with only carbons, hydrogens and single bonds is called propane. CH 3 CH 2 CH 3

Unsaturation l If a molecule contains double or triple bonds it is said to be unsaturated (meaning that it would be possible to fit in more hydrogens if the double bonds were changed to single). l Chains with one double bond take the suffix - ene. Example: ethene CH2=CH2 l Chains with one triple bond take the suffix – yne. Example: Ethyne CHΞCH

Functional Groups l Most organic chemistry involves substituents –often contain the elements O, N, S, or P –also called “functional groups”- they are the chemically functional part of the molecule, and are the non-hydrocarbon part

Functional Groups l Functional group - a specific arrangement of atoms in an organic compound, that is capable of characteristic chemical reactions. –What is the best way to classify organic compounds? By their functional groups.

Functional Groups l The symbol “R” is used to represent any carbon chains or rings l These are called alkyl groups l CH 3 - methyl group l CH 3 CH 2 - ethyl group l CH 3 CH 2 CH 2 - propyl group

Halogen Substituents l Halogenocarbons - class of organic compounds containing covalently bonded fluorine, chlorine, bromine, or iodine –General formula: R-X l Naming? Name parent as normal, add the halogen as a substituent (or prefix) -

Halogen Substituents l The more highly halogenated the compound is (I.e. the more greater the number of halogen atoms), the higher the b.p. l Few halogenoalkanes are found in nature…. –but, readily prepared and used –halothane and also the hydrofluorocarbons

Alcohols and Ethers l OBJECTIVES: –Describe the structures and naming of alcohols and ethers.

Alcohols l Alcohols - a class of organic compounds with an -OH group –The -OH functional group in alcohols is called a “hydroxyl” group; thus R- OH can represent the formula, where “R” is an alkyl group l How is this different from the hydroxide ion? (covalently bonded to the carbon- not ionically as in hydroxides)

Alcohols l Both systematic and common names l systematic: –drop the -ane ending of the parent alkane name; add ending of -anol, number the position of –OH if needed –parent is the longest chain that contains the carbon with the attached hydroxyl.

Alcohols l The hydroxyl group is given the lowest position number l Alcohols containing 2, 3, and 4 of the -OH substituents are named diols, triols, and tetrols respectively (not needed fro year 10)

Alcohols l Common names: –similar to halogenoalkanes, meaning name the alkyl group root followed by the suffix -anol –One carbon alcohol = meth- anol = methanol

Properties of Alcohols l Glycerol (propan 1,2,3 triol) - used as a moistening agent in cosmetics, foods, and drugs; also a component of fats and oils l Ethyl alcohol (ethanol) used in the intoxicating beverages; an important industrial solvent

Ethers l A class of organic compounds in which oxygen is bonded to 2 carbon chains: R-O-R is the formula l Nomenclature: The larger of the two R groups is the root and the other R group is prefixed as alkoxy- Example: CH 3 CH 2 OCH 3 methoxyethane

Alkanals and Alkanones l The C=O group is called the “carbonyl group” –it is the functional group in both alkanals and alkanones l Alkanals - carbonyl group always joined to at least one hydrogen (meaning it is always at the end!)

Alkanones l Alkanones - the carbon of the carbonyl group is joined to two other carbons (meaning it is never on the end)

Alkanals and alkanones l Nomenclature –Alkanals: identify longest chain containing the carbonyl group, then the -ane ending replaced by -anal, such as methanal, ethanal, etc. –Alkanones: longest chain with the carbonyl, then new ending of - anone; number it l propanone, 2-pentanone, 3-pentanone

Aldehydes and Ketones l Propanone (common: acetone) is a good solvent; miscible with water in all proportions l why is it a good substance used in nail-polish removers? (a powerful solvent-able to dissolve both polar & non-polar substances)

Carboxylic Acids l Also have a carbonyl group (C=O), but is also attached to a hydroxyl group (-OH) = “carboxyl” group l general formula: R-COOH –weak acids (only slightly dissociate into ions) l Named by replacing -ane with - anoic and followed by the word acid l methanoic acid; ethanoic acid

Carboxylic Acids l Abundant and widely distributed in nature, many having a Greek or Latin word describing their origin –acetic acid (ethanoic acid) from acetum, meaning vinegar –many that were isolated from fats are called fatty acids