Organic Chemistry Chapter 22

Vocabulary Organic Chemistry Carbonyl group Hydrocarbons Ketones Saturated Unsaturated Alkanes Alkenes Alkynes Cis-trans isomerism Carbonyl group Ketones Aldehydes Carboxylic acids Carboxyl group Ester Ether Amine

Saturated vs. Unsaturated Hydrocarbons Hydrocarbons are molecules composed of carbon & hydrogen Each carbon atom forms 4 chemical bonds A saturated hydrocarbon is one where all C - C bonds are “single” bonds & the molecule contains the maximum number of H-atoms An unsaturated hydrocarbon is one where at least 1 C=C bond is double.

Prefixes for # of Carbons 1 Meth 6 Hex 2 Eth 7 Hept 3 Prop 8 Oct 4 But 9 Non 5 Pent 10 Dec

Alkanes Formula: (CnH2n+2) Hydrocarbon chains where all the bonds between carbons are SINGLE bonds Name uses the ending –ane Examples: Methane, Propane, Butane, Octane Formula: (CnH2n+2)

Straight-Chain Alkanes Straight-chain alkanes contain any number of carbon atoms, one after the other, in a chain pattern - meaning one linked to the next (not always straight) C-C-C C-C-C-C etc.

Writing/drawing compounds Line formula

Normal vs Branched Alkanes NORMAL alkanes consist of continuous chains of carbon atoms Alkanes that are NOT continuous chains of carbon atoms contain branches The longest continuous chain of carbons is called the parent chain

Endings Attached carbon groups (substituents) end in –yl Methyl CH3 - Ethyl CH3CH2- Propyl CH3CH2CH2 –      3-ethylpentane

Names of branches Carbon (alkyl) groups Methyl CH3 - Ethyl CH3CH2- Propyl CH3CH2CH2 –

Branched-Chain Alkanes Rules for naming – 1. Longest C-C chain is parent 2. Number so branches have lowest # 3. Give position number to branch 4. Prefix (di, tri) more than one branch 5. Alphabetize branches (not prefix) 6. Use proper punctuation ( - and , )

Designate the Location Designate the location (number of the carbon on the parent chain) for each attached group 2-methyl 1 2 3 4 5

Name this compound 3,3-dimethylhexane

Some Simple Alkanes 2-methylpentane 3-ethylhexane 2,2-dimethylbutane

Branched-Chain Alkanes From the name, draw the structure, in a right-to-left manner: 1. Find the parent, with the -ane 2. Number carbons on parent 3. Identify substituent groups (give lowest number); attach 4. Add remaining hydrogens

Example 1: 2,2-dimethylpentane The parent chain is indicated by the ROOT of the name - “pentane”. This means there are 5 carbons in the parent chain. 1 2 3 4 5 “dimethyl” tells us that there are TWO methyl branches on the parent chain. A methyl branch is made of a single carbon atom. “2,2-” tell us that BOTH methyl branches are on the second carbon atom in the parent chain.

Example 2: 3-ethyl-2,4-dimethylheptane 1 2 3 4 5 7 6 The parent chain is indicated by the ROOT of the name - “heptane”. This means there are 7 carbons in the parent chain. “2,4-dimethyl” tells us there are TWO methyl branches on the parent chain, at carbons #2 and #4. “3-ethyl-” tell us there is an ethyl branch (2-carbon branch) on carbon #3 of the parent chain.

Example 3: 2,3,3-trimethyl-4-propyloctane The parent chain is indicated by the ROOT of the name - “octane”. This means there are 8 carbons in the parent chain. 1 2 3 4 5 7 6 8 “2,3,3-trimethyl” tells us there are THREE methyl branches - one on carbon #2 and two on carbon #3. “4-propyl-” tell us there is a propyl branch (3-carbon branch) on carbon #4 of the parent chain. 1 2 3 4 5 7 6 8

Example 4: Name the molecules shown! parent chain has 5 carbons - “pentane” two methyl branches - start counting from the right - #2 and #3 2,3-dimethylpentane parent chain has 8 carbons - “octane” two methyl branches - start counting from the left - #3 and #4 one ethyl branch - #5 name branches alphabetically 5 5-ethyl- 3,4-dimethyl 4 3 octane

Draw 2,2,4-trimethylpentane

Structural Isomerism Structural isomers are molecules with the same chemical formulas but different molecular structures n-pentane, C5H12 2-methlbutane, C5H12

However, carbons in butane (C4H10) can be arranged in two ways; four carbons in a row (linear alkane) or a branching (branched alkane). These two structures are two isomers for butane.

Your Turn Draw all possible structural isomers of C5H12

Practice

IUPAC Rules for Naming Branched Alkanes Find and name the parent chain in the hydrocarbon - this forms the root of the hydrocarbon name Number the carbon atoms in the parent chain starting at the end closest to the branching Name alkane branches by dropping the “ane” from the names and adding “yl”. A one-carbon branch is called “methyl”, a two-carbon branch is “ethyl”, etc… When there are more than one type of branch (ethyl and methyl, for example), they are named alphabetically Finally, use prefixes to indicate multiple branches

CLASSWORK ASSIGNMENT Review section 22-1 make notes on NONMENCLATURE OF ALKANES and CYCLIC ALKANES Pay attention to sample exercises!

Alkenes & Alkynes Alkenes are hydrocarbons that contain at least one carbon-carbon double bond Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond The suffix for the parent chains are changed from “ane” to “ene” and “yne” e.g. ethene, propyne the BONDS are numbered like branches so that the location of the multiple bond may be indicated

Alkenes & Alkynes: Examples ethene ethyne propene propyne butene 2-pentyne

Aromatic Hydrocarbons Cycloalkanes A cycloalkane is made of a hydrocarbon chain that has been joined to make a “ring”. Note that two hydrogen atoms were lost in forming the ring!

Aromatic Hydrocarbons Cycloalkanes The two ends of the carbon chain are attached in a ring in a cyclic hydrocarbon named as “cyclo- ____”

Aromatic Compounds and Benzene Aromatic compounds contain benzene. Benzene, C6H6 , is represented as a six carbon ring with 3 double bonds. Two possible resonance structures can be drawn to show benzene in this form.

Aromatic Hydrocarbons Benzene derivatives can have two or more substituents: 1,2-dimethylbenzene 1,3-dimethylbenzene 1,4-dimethylbenzene Can use ortho for 1,2; meta for 1,3; and para for 1,4 (page 711) C C C C

With organic compounds Isomers With organic compounds

Isomers There is a lack of rotation around a carbon to carbon multiple bond Two possible arrangements: 1. trans configuration - substituted groups on opposite sides of double bond 2. cis configuration - same side

Geometric Isomers Substituted groups are on opposite sides of the double bond (in this case, one is above, the other is below) Trans-2-butene Substituted groups are on the same side of the double bond (in this case, both are above) Cis-2-butene

Cis-Trans Isomers - Examples cis-1,3-dimethylcyclobutane cis-1,2-dichlorocyclohexane trans-1-ethyl-2-methylcyclopropane

With organic compounds Reactions With organic compounds

2C2H6(g) + 7O2(g)  4CO2(g) + 6H2O(g) Alkanes 1. Combustion reactions 2C2H6(g) + 7O2(g)  4CO2(g) + 6H2O(g) 2. Substitution reactions CH4 + Cl2  CH3Cl + HCl Methane chloromethane 3. Dehydrogenation reactions CH3CH3 CH2=CH2 + H2 Ethane ethene hv 500C

CH2 =CHCH2CH2CH3 + Br2  CH2 BrCHBrCH2CH2CH3 Alkenes & Alkynes 1. Addition reactions a. Hydrogenation CH2 =CHCH3+ H2  CH3CH2CH3 Propene Propane b. Halogenation CH2 =CHCH2CH2CH3 + Br2  CH2 BrCHBrCH2CH2CH3 Pentene 1,2-dibromopentene c. Polymerization Small molecules = large molecules Catalyst

Aromatic 1. Substitution reactions + Cl2  + HCl Catalyst = FeCl3

With organic compounds Functional Groups With organic compounds

Functional group: an atom or group of atoms within a molecule Functional Groups Functional group: an atom or group of atoms within a molecule

Functional Groups

Alcohols contain an -OH (hydroxyl) group

Halides & Carboxylic Acids contain an -X (Halogen) group F, Cl, Br, I, At contain a carboxyl (-COOH) group

Aldehydes and Ketones contain a carbonyl (C=O) group

Amines contain an amino group; nitrogen bonded to one, two, or three carbon atoms an amine may by 1°, 2°, or 3° C H 3 N Methylamine (a 1° amine) Dimethylamine (a 2° amine) Trimethylamine (a 3° amine) :

Esters & Ethers Ester: trapped carboxylic acid Ether: Trapped oxygen

Branches CnH2n+2 Alkane CnH2n+1 Alkyl group CH4 methane CH3 Methyl propane –C3H7 propyl CH3CHCH3 methylethyl

R-O-R’ ether Functional Group General Formula Name Examples   alkanone butan-2-one -COOH RCOOH alkanoic acid ethanoic acid -COOR’ RCOOR’ ester methyl ethanoate saturated ring CnH2n cycloalkane cyclohexane -X -RX haloalkane chloroethane R-O-R’ ether ethoxyethane -OH ROH alkanol ethanol (-CHO)   RCHO alkanal ethanal amine -NH2 RNH2 methylamine

Naming

Naming

Naming