Chapter 20 Organic ChemistryI. What is Organic Chemistry?

A. Organic Chemistry = chemistry of carbon containing (organic) molecules

B. Most Familiar compounds are “organic”

1) Cotton in clothing 4) Plastics

2) Gasoline 5) Drugs

3) Food 6) Dyes

C. Natural Products vs. Synthetic Organic compounds

1) Natural Products are compounds we find in the environment

a) May need to be refined or isolated from the source

b) Are starting materials for synthetic compounds

2) Synthetic Organic compounds do not occur naturally and must be synthesized from simpler compounds

D. Caffeine: an important organic molecule

E. Hydrocarbons: simplest organic molecules

N

N

N

N

O CH3

CH3

O

CH3

II. AlkanesA. Structure (Carbon always has four bonds)

1) Hydrocarbons = molecules containing only hydrogen and carbon atoms

2) Saturated = hydrocarbon containing all of the hydrogen possible (all single bonds)

3) Unsaturated = hydrocarbon with less than maximum H’s (double/triple bonds)

4) Normal Alkanes = straight chain, with no branching

5) Branched Alkanes = no longer just one chain; main chain has “branches”

6) Structural Isomers = same chemical formula, but different order of attachment; straight-chain and branched alkanes are structural isomers of each other

B. Nomenclature: systematic naming by IUPAC rules

1) Straight Chain Alkanes

a) C1 = Methane C2 = Ethane C3 = Propane C4 = Butane

b) C5-C10 = pent-, hex-, hept-, oct-, non-, dec- -ane

Saturated= Alkane

Unsaturated= Alkene

C4H10 C4H10

Generic Formula:CnH2n+2

2) Rules for naming Branched Alkanes (or drawing structure from name)

1. Find the longest chain and name it as a straight chain alkane

2. Name substituents as alkyl groups

3. Number the main chain starting from the end closest to a substituent

4. Write the name

i. Alphabetize by sub. (di-, tri-count only if part of sub. name)

ii. Order #’s from low to high; use smallest possible numbers

iii. Capitalize the first letter only

iv. Write as one word with commas and hyphens as needed

v. Complex substituents in parentheses

5-Ethyl-2,2-dimethyloctane 4-ethyl-3,6-dimethyldecane

5-(1,1-Dimethylethyl)-3-ethyloctane

11’

4-(1-Ethylpropyl)-2,3-dimethylnonane

1

1

1

C. Cycloalkanes

1) Remove 2 terminal H’s and join the terminal carbons

2) General formula = CnH2n

3) Names: prefix cyclo- is added to the n-alkane name

4) Homologous series as ring size increases by CH2

5) Not Structural Isomers of other alkanes, because different formulas

D. Reactions of Alkanes

1) Not very reactive; all bonding positions occupied by H

2) Combustion Reactions: Always make CO2 and H2O

CH3CH3 + 7/2O2 -----> 2CO2 + 3H2O

Important as energy sources: gasoline contains alkanes (octane)

3) Substitution Reactions: by halogens to make haloalkanes

CH4 + Cl2 -----> CH3Cl + HCl (Chloromethane)

New Functional Group Haloalkanes = replace H with F,Cl,Br,I on an alkane

4) Dehydrogenation Reactions: removing H makes unsaturated hydrocarbons

CH3 CH3CH2 CH2

cyclopentane

methylcyclohexaneethylcyclobutane

Cr2O3, 500 oC H H

III. AlkenesA. Structure: Hydrocarbons containing at least one double bond

1) Generic formula = CnH2n

2) Hybridization is sp2, rather than the sp3 hybridization of alkanes

3) Can have cis and trans isomers

B. Nomenclature

1) Name similarly to the alkanes, but with an –ene ending (Ethene, not Ethane)

2) Indicate the position of the double bond with a number (Structural Isomers)

CH2=CHCH2CH3 is 1-butene

CH3CH=CHCH3 is 2-butene

3) Stereoisomers = same formula/attachment, different spatial orientation (cis/trans)

C. Reactions

1) Addition Reactions = carbons can add atoms because of unsaturation

Hydrogenation: CH2=CHCH3 + H2 --------> CH3CH2CH3

Halogenation: CH2=CHCH3 + Br2 --------> CH2BrCHBrCH3

cis-2-butene

trans-2-butene

catalyst

IV. AlkynesA. Structure: Hydrocarbons containing at least one triple bond

1) Generic formula = CnH2n-2

2) Hybridization is sp, rather than the sp2 hybridization of alkenes

B. Nomenclature

1) Name similarly to the alkenes, but with an –yne ending (Ethyne, not Ethene)

2) Indicate the position of the triple bond with a number (Structural Isomers)

a) HCCCH2CH3 is 1-butyne

b) CH3CCCH3 is 2-butyne

C. Reactions

1) Addition Reactions = carbons can add atoms because of unsaturation

a) Hydrogenation: HCCCH3 + 2H2 --------> CH3CH2CH3

b) Halogenation: HCCCH3 + 2Br2 --------> CHBr2CBr2CH3

catalyst

CH3CCCH3

V. Aromatic HydrocarbonsA. Structure: must contain a six-membered ring having three double bonds

1) Benzene is the simplest aromatic; sp2 hybridization at every carbon

2) There are two equivalent resonance forms; a circle in the center is a shortcut

B. Nomenclature: number and name the substituents as prefixes to “benzene”

1) There are three structural isomers of disubstituted benzenes

2) An older system called them ortho-, meta-, and para-

C. Reactions

1) Very unreactive compared to other hydrocarbons: resonance stabilization

2) Substitution of hydrogen atoms is possible with the right catalysts

+ CH3ClAlCl3

+ Cl2 FeCl3

Cl

VI. Alcohols, Aldehydes, and Ketones A. Structure of Alcohols: replace an -H on a hydrocarbon with an –OH

Short chain alcohols are water soluble (Hydrogen Bonding)

Most hydrocarbons are not water soluble because they are non-polar

B. Nomenclature

1) Modify the alkane name by dropping –e and adding –ol

2) Name based on longest chain containing -OH

3) Number each carbon starting from the closest to –OH

C. Reactions: Oxidation to Aldehydes and Ketones

1) Classifying alcohols: Primary at the end of a chain; Secondary within the chain

2) An Aldehyde is an oxidized Primary Alcohol (reduced aldehyde)

3) A Ketone is an oxidized Secondary Alcohol (reduced ketone)

4) Aldehydes are named with –al endings, Ketones are named with –one endings

CH3CH2CH2OH1-butanol

Primary alcohol

Secondary alcohol

C

O

R H

oxidation

reductionRCH2OH

C O

R

R'CH OH

R

R'Na2Cr2O7

H2SO4, H2O

VII. Carboxylic Acids and DerivativesA. Structure: Carboxylic Acids contain an O=C—OH ; a complicated functional group

B. Nomenclature

1) Assign number 1 to carboxy carbon and number longest chain including it

2) Replace –ane ending of an alkane with –oic acid ending

3) Carboxylic acids have priority over any other functional group studied

C. Reactions: Carboxylic Acids can become several related functional groups

1) Addition-Elimination Reaction: New molecule adds, while OH leaves

H3C OH

O

H3C Cl

O

H3C

O

H3C O

O

H3C NH2

O

SOCl2 CH3OH

NH3

H3C OH

O

CH3O

O

Acyl Halide

Anhydride

Ester

Amide

CH3

Carboxylic Acid

VIII. Amines and EthersA. Amines are derivatives of Ammonia, in which hydrogen is replaced by alkyl groups

1) Primary Amine: Only one H atom is replaced

2) Secondary Amine: Two H atoms are replaced

3) Tertiary Amine: All three H atoms are replaced

B. Can be Aromatic or Heteroaromatic

C. Basic due to nitrogen lone pair

D. Ethers are Derivatives of Water, in which both Hydrogens are replaced by alkyl groups

1) Related to alcohols, in which only one H atom of water is replaced

2) Fairly Unreactive; Similar polarity to the alkanes, unless very small

3) Non-polar and unreactive—much like alkanes

N Triethylamine

NH2Butylamine

NH

Ethylmethylamine

Aminobenzene (Aniline)

N

Pyridine

NH2

O Diethyl Ether

VIII. PolymersA. Long-chain molecules built from many small molecule units (monomers)

1) Plastics, synthetic fibers (nylon), and many other materials are polymers

2) One of the most important chemical discoveries effecting daily life

B. Types of Polymerizations

1) Addition Polymerization = identical monomers add together with no biproducts

Polymers based on alkenes are common examples

2) Condensation Polymerization = two molecules add, with a biproduct given off

3) Co-polymer = 2 different monomers, Homopolymer = 1 type of monomer

C C C CC

monomer

C C C C C CC

polymer

O

OH

O

HO

+HOCH2CH2OH

O

O

O

CH2CH2O

+ H2O Dacron Polyester