AROMATIC SUBSTITUTION REACTIONS . NOMENCLATURE. Learn Nomeclature Either on Your Own or Use the Organic Nomeclature Software. 1-bromo-3-nitrobenzene. methylbenzene. (toluene). 1-chloro-3-methylbenzene. 1,4-dimethylbenzene. SOME SPECIAL NAMES. toluene. aniline. anisole.
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AROMATIC SUBSTITUTION REACTIONS
Learn Nomeclature Either on Your Own or Use the Organic Nomeclature Software 1-bromo-3-nitrobenzene methylbenzene (toluene) 1-chloro-3-methylbenzene 1,4-dimethylbenzene
SOME SPECIAL NAMES toluene aniline anisole phenol o-xylene m-xylene benzoic acid p-xylene
ortho, meta and para Positions m-nitrotoluene 3-nitrotoluene ipso 1 o- ortho 6 2 1-methyl-3-nitrobenzene meta m- 5 3 4 para p-dichlorobenzene p- 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
BENZENE RESONANCE Review Sections 6.8 - 6.14 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 . . . . H H H H All 2p orbitals overlap equally.
BENZENE Isodensity surfaces - electron potential mapped in color. (van der Waal’s) Highest electron density is red. Color adjusted to enhance the pi system. Note the symmetry.
BENZENE - DETERMINATION OF RESONANCE ENERGY cyclohexatriene (hypothetical) benzene RESONANCE ENERGY 36 kcal/mol cyclohexene -49.8 kcal/mol -85.8 kcal/mol (calculated) -28.6 kcal/mol cyclohexane
The “Double Bonds” in a Benzene Ring Do Not React Like Others Alkene Benzene no reaction + + no reaction + + no reaction + + no reaction + +
Benzene is a Weak Base and Poor Nucleophile Stronger base + Readily donates electrons to an electrophile. alkene + Donation of electrons would interrupt ring resonance (36 kcal / mole). Weaker base A strong electrophile is required - and often a catalyst. benzene
Benzene Reactivity Benzene requires a strong electrophile and a catalyst …..and then it undergoes substitution reactions, not addition. + + catalyst substitution compare: + no catalyst addition
Some Substitution Reactions of Benzene Halogenation + Friedel-Crafts Alkylation + Friedel-Crafts Acylation + - + + Nitration + - Sulfonation +
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
Oxidation of Alcohols primary alcohol aldehyde carboxylic acids RCH2OH RCHO RCOOH secondary alcohols ketones RCHOHR’ RC=OR’ tertiary alcohols No Reaction
Ethanol is being tested in selected areas as a fuel for automobiles Source: AP/Wide World Photos
STRUCTURE Aldehyde Ketone
Cinnamaldehyde produces the characteristic odor of cinnamon Source: Visuals Unlimited
IUPAC Nomenclature of Ketones • 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 Do the ketonessection of Organic Nomenclature program!
EXAMPLES 2-Pentanone 4-Ethyl-3-hexanone
3-Isopropylcyclopentanone or 3-(1-Methylethyl)cyclopentanone
KETONES 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!
Example of Common Names Methyl propyl ketone Diethyl ketone
SPECIAL CASES diphenyl ketone dimethyl ketone benzophenone acetone A common laboratory solvent and cleaning agent methyl phenyl ketone KNOW THESE acetophenone
IUPAC Nomenclature of Aldehydes • 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 Do the aldehydessection of Organic Nomenclature program.
EXAMPLES aldehyde group is always carbon 1 pentanal 3 1 4 2 2-chloro-3-methylbutanal
RECOGNIZE THESE Common Names of the Aldehydes
SPECIAL CASES formaldehyde benzaldehyde KNOW THESE acetaldehyde
Computer-generated space-filling model of acetylsalicylic acid (aspirin) Source: Photo Researchers, Inc.