AROMATIC SUBSTITUTION REACTIONS REACTIONS

NOMENCLATURE

Learn Nomeclature Either on Your Own Learn Nomeclature Either on Your Own or Use the Organic Nomeclature Software methylbenzene 1-chloro-3-methylbenzene (toluene) 1-bromo-3-nitrobenzene 1,4-dimethylbenzene

SOME SPECIAL NAMES tolueneanilineanisole o-xylenem-xylene p-xylene phenol benzoic acid

ipso ortho meta para ortho, meta and para Positions m-nitrotoluene 3-nitrotoluene 1-methyl-3-nitrobenzene o- m- p p-dichlorobenzene 1,4-dichlorobenzene

Compounds containing aromatic rings are often used in dyes, such as these for sale in a market in Nepal Source: Getty Images

REVIEW OF BENZENE PROPERTIES

Figure 22.11: The structure of benzene

BENZENE RESONANCE Review Sections KEKULE STRUCTURES Resonance Energy = 36 Kcal / mole All bonds are equivalent The ring is symmetric. Bond lengths are between a single and a double bond. Very Stable Less reactive than other groupings of atoms.

H H HH H H All 2p orbitals overlap equally.

BENZENE Isodensity surfaces - electron potential mapped in color. (van der Waal ’ s) Color adjusted to enhance the pi system. Highest electron density is red. Note the symmetry.

cyclohexatriene (hypothetical) benzene cyclohexene cyclohexane RESONANCE ENERGY 36 kcal/mol kcal/mol (calculated) kcal/mol kcal/mol BENZENE - DETERMINATION OF RESONANCE ENERGY

REACTIVITY

The “ Double Bonds ” in a Benzene Ring Do Not React Like Others AlkeneBenzene ++ no reaction ++ no reaction + + no reaction + + no reaction

+ + Stronger base Weaker base Readily donates electrons to an electrophile. Donation of electrons would interrupt ring resonance (36 kcal / mole). A strong electrophile is required - and often a catalyst. Benzene is a Weak Base and Poor Nucleophile alkene benzene

Benzene requires a strong electrophile and a catalyst …..and then it undergoes substitution reactions, not addition. + + Benzene Reactivity substitution catalyst + compare: addition no catalyst

Some Substitution Reactions of Benzene Halogenation Friedel-Crafts Alkylation Friedel-Crafts Acylation Nitration Sulfonation

Blood Alcohol Level

Alcohols and Water alcohols are “monosubstituted” water, ROH, hydrocarbon radical, R, substituted for one of the hydrogen atoms in water, HOH alcohols form hydrogen bonds to other alcohol molecules, increasing boiling point, and to water, making them very soluble in water

Classes of Alcohols

Oxidation of Alcohols primary alcohol  aldehyde  carboxylic acids RCH 2 OH  RCHO  RCOOH secondary alcohols  ketones RCHOHR’  RC=OR’ tertiary alcohols  No Reaction

Large Molecules Containing Alcohol Groups

More Large Molecules Containing Alcohol Groups

Ethanol is being tested in selected areas as a fuel for automobiles Source: AP/Wide World Photos

ALDEHYDES AND KETONES I

Aldehyde Ketone STRUCTURE

Cinnamaldehyde produces the characteristic odor of cinnamon Source: Visuals Unlimited

NOMENCLATURE

Choose the longest continuous carbon chain that contains the carbonyl carbon Number from the end of the chain closest to the carbonyl carbon Ketone ending is -one IUPAC Nomenclature of Ketones Do the ketones section of Organic Nomenclature program!

2-Pentanone EXAMPLES 4-Ethyl-3-hexanone

3-Isopropylcyclopentanone or 3-(1-Methylethyl)cyclopentanone

Common, or Trivial, Names Name each group attached to the carbonyl group as an alkyl group Combine into a name, according to the pattern: alkyl alkyl ’ ketone NOTE: This is not all one word! KETONES

Methyl propyl ketone Example of Common Names Diethyl ketone

acetone dimethyl ketone A common laboratory solvent and cleaning agent SPECIAL CASES benzophenone diphenyl ketone acetophenone methyl phenyl ketone KNOW THESE

Choose the longest continuous carbon chain that contains the carbonyl carbon Number from the end of the chain closest to the carbonyl carbon (carbon #1!) Aldehyde ending is -al IUPAC Nomenclature of Aldehydes Do the aldehydes section of Organic Nomenclature program.

EXAMPLES pentanal 2-chloro-3-methylbutanal always carbon 1 aldehyde group is

Common Names of the Aldehydes RECOGNIZE THESE

SPECIAL CASES formaldehyde acetaldehyde benzaldehyde KNOW THESE

Figure 22.13: Some common ketones and akdehydes

Figure 22.14: Some carboxylic acids

Computer-generated space-filling model of acetylsalicylic acid (aspirin) Source: Photo Researchers, Inc.