Organic Chemistry

Organic Chemistry • Alcohols • Aldehydes and Ketones • Carboxylic Acids • Esters • Polymers • Saturated Hydrocarbons • Petroleum • Reactions of Alkanes • Unsaturated Hydrocarbons • Aromatic Hydrocarbons

Saturated Hydrocarbons - When carbon has four bonds, it has a tetrahedral arrangement. • Hydrocarbons are molecules of carbon and hydrogen, like methane. • Methane • Formula: CH4

Saturated Hydrocarbons • Alkanes are hydrocarbons with only single bonds. • A straight-chain alkane has a long chain of carbons bonded to each other with hydrogen atoms around the outside. • Example: propane has three carbon atoms and 8 hydrogen atoms:

Saturated Hydrocarbons • Formulas: For each carbon that is added in an alkane, there are two more hydrogen atoms in the compound. • A CH2 group is added from one compound in the series to the next. CH3 – (CH2) m – CH3 • Memorize the first ten prefixes for naming alkanes: meth, eth, prop, but, pent, hex, hept, oct, non, dec

Saturated Hydrocarbons • Branched-Chain Alkanes • A substituent is an atom or group that attaches to a carbon. • Name alkyl groups by removing “-ane” and adding “-yl” • Methyl group: CH3 • An alkane substituent is an alkyl group. • A chain with one or more substituent is branched.

Saturated Hydrocarbons • Naming alkanes with the IUPAC rules. • Step 1. Find the longest continuous chain of carbons (it doesn’t have to be straight). (Draw a line through these carbons if it’s helpful.) Assign an “alkane” name according to the number of carbons in this chain.

Saturated Hydrocarbons • Step 2. All carbons not in this main chain are “branches” connected to the main chain. Name each branch using the corresponding prefix with a “–yl” ending. 1 carbon - “methyl” 2 carbons - “ethyl” 3 carbons - “propyl”

Saturated Hydrocarbons “2, 2, 3 – trimethyl pentane” Step 3. Number the carbons in the main chain so that the branch(es) have the lowest possible numbers assigned to them. Assign each branch a number corresponding to where it attaches to the main chain.

Petroleum • Petroleum and natural gas were formed from decayed plants over 500 million years old. • It is called “buried sunshine” because the energy in it originally came from the sun. • Plants used photosynthesis to store energy. • Petroleum contains hydrocarbons with chains containing 5-25 carbon atoms. • Natural gas contains methane, ethane, propane and butane.

Combustion Reactions In a combustion reaction, a hydrocarbon (or another fuel) reacts with O2 to make CO2 and H2O. 2C4H10 + 13O2 8CO2 + 10H2O

Combustion Reactions CO2 + H2O 5 O2 3 4 Write the balanced equation for the combustion of propane: C3H8 +  1. Write O2 on the left 2. Write CO2 and H2O on the right. 3. Balance.

Substitution Reactions hv • In substitution reactions, hydrogen atoms are replaced by different atoms. CH4 + Cl2 CH3Cl + HCl • The hv represents ultraviolet radiation.

Dehydrogenation Reactions H H C C H H Cr2O3 500 °C In a dehydrogenation reaction, hydrogen atoms are removed and a double or triple bond forms. CH3CH3 + H2

Unsaturated Hydrocarbons H H C C H H • Alkenes have double bonds. • Naming: add “-ene” • Example: “ethene”

Unsaturated Hydrocarbons H H H H H H C C C C H H H H • Naming alkenes: Name them like alkanes, but use a number to show the location of the double bond. • Because there’s only one place for the double bond on ethene and propene, you don’t need a number. • Example: 2-butene

Unsaturated Hydrocarbons CH CH • Alkynes have triple bonds. • Naming: add “-yne” • Example: C2H2 “ethyne”

Unsaturated Hydrocarbons Pt Catalyst + H2 CH3CH2CH3 + Br2 • In addition reactions, atoms are added across a double or triple bond. • Hydrogenation is an addition reaction. H2 is added. • Halogenation is an addition reaction. A halogen (group 7A) is added.

Aromatic Hydrocarbons H H H C C C C C H H C • Aromatic hydrocarbons smell nice, like wintergreen and cinnamon. • Most aromatic hydrocarbons contain a benzene ring. • Benzene is a 6-carbon ring with three double bonds (C6H6). H

Aromatic Hydrocarbons When two or more structures can be drawn for a molecule, resonance occurs.

Aromatic Hydrocarbons In reality, there are no double bonds in benzene. The electrons are shared evenly around the ring. This is a more accurate way to represent benzene:

Aromatic Hydrocarbons • Benzene is called a “phenyl” group when it is a side group on an alkane. • Example: 3-phenylnonane

Aromatic Hydrocarbons • Naming benzene with one side group: “Benzene” + “Side group name” • Example: Methylbenzene

Aromatic Hydrocarbons • Naming benzene with two side groups: Name them like alkanes, but assign one group the #1: • Example: 1,3-dimethyl benzene

Aromatic Hydrocarbons • Common names for disubstituted benzenes: • 1, 2 position is “orotho” (o) • 1, 3 position is “meta” (m) • 1, 4 position is “para” (p)

Alcohols • Functional groups are groups of atoms that are capable of characteristic chemical reactions. • For example, the functional group of a carboxylic acid is circled below, a COOH group. • The “R” stands for the “rest” of the molecule.

Alcohols • An alcohol is an organic compound with an “-OH” group. • The “-OH” group is called a hydroxyl group. • There are three kinds of alcohols: 1). Primary alcohol – one “R” group attached to the C-OH 2). Secondary alcohol – two“R” groups attached to the C-OH 3). Tertiary alcohol – three “R” groups attached to the C-OH

Alcohols Primary Secondary Tertiary

Alcohols • Naming alcohols: Drop the “e” from the alkane name and “-ol” • Example: Methanol.

Alcohols • Properties • Ethanol is produced by fermentation, which is the digestion of sugar by yeast. Alcoholic beverages such as beer are made by this process. • Methanol is used to make many materials—plastics, fibers, etc.

Aldehydes and Ketones A carbonyl group is a functional group with a group. An aldehyde has a carbonyl group, where the carbon is bonded to one or two hydrogen atoms. It has the general formula: RCHO.

Aldehydes and Ketones A keytone has a carbonyl group on a carbon that is bonded to two other carbons. General formula: RCOR

O C CH3 CH2 CH2 CH3 Aldehydes and Ketones • IUPAC Naming: • Aldehydes: alkane name minus “e” plus “al”: • Methane Methanal • Keytones: alkane name minus “e” plus “anone.” Write the number of the carbon that has the carbonyl group first: “2-pentanone”

Carboxylic Acids Carboxylic acids have the general formula RCOOH They ionize slightly when dissolved in water:

Carboxylic Acids • IUPAC Naming: • Add “-oic acid” • “Ethanoic acid” • Carboxylic acids don’t smell good. • Vinegar contains ethanoic acid.

Esters Esters Esters have the general formula RCOOR

Esters “Methyl ethanoate” o H o H H H C H + H O C H H C C O H O H H C C O H H H H H • Esters can be made by a reaction between a carboxylic acid and alcohol. • Esters smell good, and make the smells in bananas, oranges and other fruits and flowers.

Polymers • Polymers are made from small molecules, called monomers. • Ethene can react with itself, creating an addition polymer. • This reaction is called an addition reaction. Many ethene add onto the growinig polymer chain to make a very long molecule.

Polymers EtheneGrowing polymer chainPolyethylene

Organic Chemistry