Unit 3Organic Chemistry Chemistry 2202

Introduction Organic Chemistry is the study of the molecular compounds of carbon. eg. CH 4 CH 3 OHCH 3 NH 2 Organic compounds exclude oxides of carbon and ions containing carbon. ie. CO, CO 2, KCN, CaCO 3 are NOT organic compounds!!

History of Organic Chemistry Organic chemistry can be traced back to ancient times when medicine men extracted chemicals from plants and animals to treat members of their tribes Organic chemistry was first defined as a branch of modern science in the early 1800's by Jon Jacob Berzelius

Berzelius believed in Vitalism - organic compounds could only originate from living organisms through the action of some vital force organic compounds originate in living or once-living matter inorganic compounds come from "mineral" or non-living matter

In 1828, Friedrich Wöhler discovered that urea - an organic compound - could be made by heating ammonium cyanate (an inorganic compound). NH 4 OCN (aq)  (NH 2 ) 2 CO (s) inorganic organic

organic chemistry branched into disciplines such as polymer chemistry, pharmacology, bioengineering and petro-chemistry 98% of all known compounds are organic

The huge number of organic compounds is due mainly to the ability of carbon atoms to form stable chains, branched chains, rings, branched rings, multiple rings, and multiple bonds (double and triple bonds) to itself and to many other non-metal atoms.

Sources of Organic Compounds 1. Carbonized Organic Matter - fossil fuels such as coal, oil, and natural gas - basis for the petrochemical industry 2. Living Organisms eg: - penicillin from mold - ASA from the bark of a willow tree

3. Invention - antibiotics, aspirin, vanilla flavoring, and heart drugs are manufactured from organic starting materials - plastics

Structural Isomers Structures that have the same molecular formula but different structural formulas are called structural isomers eg. C 4 H 10 Practice: Draw all structural isomers of C 5 H 12 and C 6 H 14

Structural Isomers structural isomers have the same chemical formula but have different chemical and physical properties.

Classifying Organic Compounds Organic Compounds Hydrocarbons Hydrocarbon Derivatives

hydrocarbons consist of carbon and hydrogen atoms only eg. Methane - CH 4 hydrocarbon derivatives have one or more hydrogen atoms replaced by another nonmetallic atom eg. bromomethane - CH 3 Br methanol - CH 3 OH

Hydrocarbons Aliphatic Hydrocarbons Aromatic Hydrocarbons (benzene based) AlkAnes AlkEnes AlkYnes

aliphatic hydrocarbons have carbon atoms bonded in chains or rings with only single, double, or triple bonds aromatic hydrocarbons contain at least one 6 carbon benzene ring

Aliphatic Hydrocarbons 1.Alkanes Alkanes are hydrocarbons that have only single bonds between carbon atoms general formula C n H 2n+2 eg. C 3 H 8 C 6 H 14

IUPAC prefixes Prefix# of carbon atoms meth1 eth2 prop3 but4 pent5 hex6 hept7 oct8 non9 dec10

Complete this table for the first 10 alkanes methaneCH 4 ethane propane

A series of compounds which differ by the same structural unit is called a homologous series eg. each successive member of the alkanes increases by CH 2

Representing Alkanes (4 ways) 1. Structural formulas eg. propane H – C – C – C – H H HH H HH

Hydrogen atoms may be omitted from structural formulas eg. propane – C – C – C –

2. Condensed Structural Formula eg. propane CH 3 -CH 2 -CH 3

3. Line Structural Diagrams eg: propane (the endpoint of each segment is a carbon atom)

4. Expanded Molecular Formulas eg. propane CH 3 CH 2 CH 3

Alkyl Groups An alkyl group has one less hydrogen than an alkane. General Formula: C n H 2n + 1 To name an alkyl group, use the prefix to indicate the # of carbon atoms followed by the suffix –yl eg. -C 7 H 15 heptyl

Alkyl Groups methyl -CH 3 ethyl -C 2 H 5 or -CH 2 CH 3 propyl -C 3 H 7 or -CH 2 CH 2 CH 3

Alkyl Groups Branched alkanes are alkanes that contain one or more alkyl groups eg.

Naming Branched Alkanes 1. Find the longest continuous chain of carbons and name it using the alkane name. This is the parent chain. 2. Number the carbons in the parent chain starting from the end closest to branching. These numbers will indicate the location of alkyl groups.

Naming Branched Alkanes 3. List the alkyl groups in alphabetical order. Use Latin prefixes if an alkyl group occurs more than once. (di = 2, tri = 3, tetra = 4, etc.) 4. Use a number to show the location of each alkyl group on the parent.

Naming Branched Alkanes 5. Use commas to separate numbers, and hyphens to separate numbers and letters.

Naming Branched Alkanes eg ethyl methyl 4-ethyl-3-methylheptane

Naming Branched Alkanes Practice: p #’s

Alkenes and Alkynes saturated compounds contain only single bonds between carbon atoms eg. alkanes saturated compounds have the maximum number of hydrogen atoms bonded to carbon atoms

Alkenes and Alkynes unsaturated compounds contain double or triple bonds between carbon atoms eg. alkenes and alkynes

Alkenes and Alkynes General Formulas: AlkenesC n H 2n AlkynesC n H 2n - 2

Naming Alkenes and Alkynes 1. Name the longest continuous chain that contains the double/triple bond. Use the smallest possible number to indicate the position of the double or triple bond.

Naming Alkenes and Alkynes 2. Branches are named using the same rules for alkanes. Number the branches starting at the same end used to number the multiple bond.

Naming Alkenes and Alkynes p. 347 #’s p. 354 #’s 28 & 29

Cyclic Hydrocarbons Pp. 356 – 358 questions 30 & 31

cyclopentane methyl ethyl 1-ethyl-3-methylcyclopentane 3-ethyl-1-methylcyclopentane 1 2 3

methyl 1,2,3,4-tetramethylcyclohexane

Aromatic Compounds Aromatic hydrocarbons contain at least one benzene ring. The chemical formula for benzene, C 6 H 6, was determined by Michael Faraday in Structural formula was determined by August Kekulé in 1865.

Aromatic Compounds benzene ring consists of six carbon atoms, each of which is bonded to a hydrogen atom (Try to draw this!!) C 6 H 6 can be drawn with alternating single and double bonds.

Aromatic Compounds While C=C double bonds are shorter than C-C single carbon bonds, x-ray crystallography shows that all six C-C bonds in benzene are the same length. Benzene molecules behave like alkanes in chemical reactions, not like the alkenes

Aromatic Compounds Kekulé thought benzene could exist in two forms and used the idea of resonance to explain its structure. The resonance structure is an average of the electron distributions.

Aromatic Compounds or

Aromatic Compounds bonding electrons that were thought to be in the double bonds are delocalized and shared equally over the 6 carbon atoms the bonds in benzene are like “1 ½” bonds – somewhere between single and double.

Naming Aromatic Compounds an alkyl benzene has one or more H atoms replaced by an alkyl group. name the alkyl groups, using numbers where necessary, followed by the word benzene.

Aromatic Compounds methylbenzene propylbenzene ethylbenzene

Aromatic Compounds 1,3-dimethylbenzene 1,4-dimethylbenzene 1,2-dimethylbenzene

Aromatic Compounds ortho- means positions 1 and 2 and is represented by an italicized "o" meta- means positions 1 and 3 and is represented by an italicized "m" para- means positions 1 and 4 and is represented by an italicized "p"

Aromatic Compounds m-dimethylbenzene p-dimethylbenzene o-dimethylbenzene

Aromatic Compounds Benzene is treated as a branch if it is not attached to the terminal carbon of an alkyl group Benzene as a branch is called phenyl

Aromatic Compounds propylbenzene 2-phenylpropane

Aromatic Compounds

p. 361 #’s 32 – 35 Hydrocarbons Practice pp. 363, 364 #’s 4 – 9 Test!!

Hydrocarbon Derivatives Hydrocarbon Derivatives have one or more H atoms replaced by another nonmetallic atom Types of derivatives: carboxylic acids organic halides esters alcohols ethers aldehydes ketones

Hydrocarbon Derivatives A functional group is the reactive group of atoms that gives a family of derivatives its distinct properties. The general formula for a derivative is R - functional group where R stands for any alkyl group. Bonded to

Hydrocarbon Derivatives eg.ALCOHOLSR-OH ethanolC 2 H 5 OH propanolC 3 H 7 OH CARBOXYLIC ACIDS R-COOH ethanoic acidCH 3 COOH propanoic acidC 2 H 5 COOH hydroxyl group carboxyl group

Hydrocarbon Derivatives Types of derivatives (See p. 378) Alcohols – pp Ethers – pp. 394 – 396 Aldehydes & Ketones – pp. 402,403 Carboxylic Acids – pp.405, 406 Alkyl Halides – pp. 390, 391 Esters – pp. 410, 411