Introduction to Organic Chemistry Beginning the story of carbon

Petroleum – the Primary Source Hydrocarbons - Compounds containing only carbon and hydrogen “Saturated” hydrocarbons are called alkanes – As many hydrogens in the molecule as possible

CH 4 Methane

Major Sources of Methane Rice Paddies Cattle Decaying Garbage Natural Gas –B. P. – 161.5

C2H6C2H6 CH 3 Ethane

Ethane Facts Component of natural gas –B. P. – 88.6

C3H8C3H8 CH 3 CH 2 CH 3 Propane

Commercial Uses LP (liquid petroleum) Gas –Home heating –Cooking –Recreational Uses Outdoor grills Gas Fireplaces –B. P. - 42

C 4 H 10 CH 3 CH 2 CH 2 CH 3 CH 3 (CH 2 ) 2 CH 3 Butane

Butane facts Easily liquefied, vaporized at room temp –B. P Pocket lighters Portable, rechargeable torches

The rest of the family of alkanes General Formula: C n H 2n+2 Prefixes: –1 Meth6 Hex –2 Eth 7 Hept –3 Prop 8 Oct –4 But 9 Non –5 Pent 10 Dec

Ways to show Molecules Molecular formula: C 2 H 6 –Shows only the number of each element Lewis Dot Structure –Shows structure and ALL valence electrons –Must have one dot for each electron H H.... H:C:C:H.... H H

More ways to show molecules Condensed structural formula –Shows or specifically indicates the location of each element CH 3 CH 3 - Bonds are implied, not shown

Still more ways…. Extended Structural formula –Hybrid of condensed structural and Lewis dot –Replaces pair of electrons with a solid line –Chemists sometimes mix condensed and extended structural formulas, showing some but not all bonds H H | | H-C-C-H CH 3 – CH 3 | | H H

Isomers: Same molecular formula, different structure and properties

CH 3 CH 2 CH 2 CH 3 or CH 3 CH CH 3 CH 3 Butane: First Hydrocarbon with Isomers

Groups as Substituents Methane becomes methyl Ethane becomes ethyl Propane becomes propyl Butane becomes butyl Pentane becomes pentyl Etc. The generalized substituent: R- = any alkyl group

Numbers of Isomers 4 carbons – 2 5 carbons – 3 6 carbons – 5 7 carbons – 9 8 carbons – 18 9 carbons – carbons - 75

Naming Isomers CH 3 -CH 2 -CH 2 -CH 3 1-butane The 1 makes clear that all the carbons are in a line CH 3 – CH – CH 3 2-methyl propane | CH 3

Note: Carbon’s Four Bonds! H | CH 3 – C – CH 3 vs. CH 3 -CH 2 -CH 2 -CH 3 | CH 3 On the second carbon in the row, we removed an H, so we could hook on a C and still have 4 and only 4 bonds on each C

Systematic names Developed by IUPAC (International Union of Pure and Applied Chemistry) –Identify and name the longest carbon chain –Number it from one end to the other so that groups attached will have the lowest numbers possible

Example CH 3 CH CH 2 CH 2 CH 2 CH 3 | CH 3 2-methylhexane, not 5-methylhexane

More Complex CH 3 CH CH CH 2 CH 2 CH 2 CH 3 | | CH 3 CH 3 2,3-dimethylheptane

As we learn “functional groups” (the general name for other atoms or groups we can hook onto carbon), we will practice additional names.

Other Hydrocarbon Families Saturated hydrocarbons = “Alkanes” Other types of hydrocarbons also group in families Basically, the prefix of the compound tells the number of carbons, always The ending of the name tells about the bonding This makes learning all of them EASY!

Unsaturated Compounds: Alkenes Two or more carbons At least one double bond –May be located anywhere in the chain of carbon atoms

C 2 H 4 CH 2 =CH 2 Ethene (also called ethylene)

C 3 H 6 CH 2 =CH-CH 3 Propene (or propylene)

C 4 H 8 Multiple Isomers: CH 2 =CH-CH 2 -CH 3 or CH 3 -CH=CH-CH 3 which can be CH 3 CH 3 CH 3 H C = C or C=C H H H CH 3 or CH 3 C=CH 2 CH 3

Butene Isomer Names n-butene or 1-butene 2 – butene –Cis (methyls on same side) –Trans (methyls on opposite sides) Cis and trans are geometric isomers –iso-butene or methyl propene Vs. 1 and 2 butene, structural isomers

General formula for alkenes C n H 2n

Then there’s the triple bond: Alkynes C 2 H 2 HC CH Ethyne, also called acetylene

General formula for Alkynes: C n H 2n-2

Isomers of Alkynes Positional or structural isomers only (location along chain, branching) –Because, alkynes are linear

Cycloalkanes CyclopropaneCH2 – CH2 CH2 CyclobutaneCH2 – CH2 CH2 – CH2

And more….. CyclopentaneCH2 – CH2 CH2

Cyclohexane CH2 CH2 CH2 CH2 CH2 “Boat” CH2 CH2 CH2 CH2 “Chair”

One more way to illustrate: Hydrocarbon frameworks can be illustrated by bent lines, each bend being a carbon and its associated hydrogens: = pentane = cyclopropane

Aromatics- cyclics with double bonds Benzene – Kekule’s dreamCH CHCHCHCH  CHCHCHCHCH As a substituent, abbreviated Ar for “Aryl”

Cyclic Aromatics All Bond lengths are equal Do not easily undergo addition reactions “Compromise” structure: CHCHCH

Adding Functional Groups Halogens –Substitution for hydrogen with alkanes, aromatics RCH 3 + Cl 2  RCH 2 Cl + HCl ArH + Cl 2  ArCl + HCl –Addition to double bonds RCH=CHR + Cl 2  RCHCl-CHClR

Compounds with Oxygen Alcohols: R – OH –Addition of water across a double bond or replacement of a halogen Aldehydes: C=O at the end of a molecule R – C=OH Ketones: C=O in the middle of a molecule R – C=O – R

More Oxygen Compounds Organic Acids: C=O-OH –The H is capable of ionizing to give R – C=O – O - and H + Esters: combine an acid and an alcohol: R – C=O – O – R Ethers: use a singly-bound oxygen to join two alkyl groups: R – O - R

Versatile nitrogen: Amines A –NH 2 group can substitute for a halogen: R – CH 2 – NH 2 But also, nitrogen can have one, two, or three alkyl groups hooked to it: –R – NH 2 primary amine (1 o ) –R 2 – NH secondary amine (2 o ) –R 3 – N tertiary amine (3 o )

Amides: Acids plus amines As long as an amine has at least one hydrogen on nitrogen, it can react with an organic acid to produce an amide and water R – C=O-OH + R’NH 2  RC=ONHR’ + H 2 O

Esters: Acids plus alcohols Similar reaction to Amides: RCOOH + R’OH  RCOOR’ + H 2 O

Amino Acids: Building blocks of us Amino Acids have both an amino group (NH2) and an acid group (COOH). CH 3 –CH – COOH | NH 2 Amino Acids link together to make up proteins in the body

Basic Organic Reactions Addition to an olefin (alkene) CH 2 =CH 2 + HCl  CH 3 -CH 2 Cl –Hydrohalogenation CH 2 =CH 2 + Br 2  CH 2 Br-CH 2 Br –Halogen addition CH 2 =CH 2 + H 2  CH 3 – CH 3 –Reduction

Basic Organic Reactions, con’t Replacement/substitution CH 3 -CH 2 Cl + KOH  CH 3 -CH 2 OH + KCl CH 3 -CH 2 OH + HCl  CH 3 -CH 2 Cl + H 2 O CH 3 CH 3 + Cl 2  CH 3 CH 2 Cl + HCl Dehydration CH 3 -CH 2 OH  CH 2 =CH 2 + H 2 O

Basic Organic Reactions, con’t Esterification CH 3 COOH + CH 3 OH  CH 3 COOCH 3 + H 2 O Amidation CH 3 COOH + CH 3 NH2  CH 3 CONHCH 3 + H 2 O

Polymers: Our Plastic World Addition polymers: link together by combining double-bonded materials –Ethylene CH 2 =CH 2  Polyethylene –Propylene CH 2 =CH  Polypropylene | CH 3

More addition polymers Styrene CH 2 =CH  polystyrene | Vinyl Chloride CH 2 =CHCl - PVC

And then Condensation Polymers Polyester (like Dacron®) HOOC COOH + HOCH 2 CH 2 OH Polyamide (like nylon) H 2 N (CH 2 ) 6 NH 2 + HOOC (CH 2 ) 4 COOH or H 2 N (CH 2 ) 5 COOH