Organic Organic ChemistryChemistry

CE 541CE 541

Aromatic HydrocarbonsAromatic Hydrocarbons

They are hydrocarbons that include They are hydrocarbons that include benzene and compounds containing benzene and compounds containing aliphatic or aromatic groups attached to aliphatic or aromatic groups attached to aromatic rings.aromatic rings.

Benzene is the simplest aromatic Benzene is the simplest aromatic hydrocarbon (hydrocarbon (C6H6C6H6))

More recently, the following is used to More recently, the following is used to represent the structure of Benzenerepresent the structure of Benzene

NomenclatureNomenclature

The monocyclic aromatic hydrocarbons are The monocyclic aromatic hydrocarbons are named as derivatives of the parent benzene. named as derivatives of the parent benzene. Trivial names of some of the compounds are Trivial names of some of the compounds are still recognized by the IUPACstill recognized by the IUPAC

TT oluene oluene o-xyleneo-xylene m-xylenem-xylene p-xylenep-xylene

(ortho-xylene)(ortho-xylene) (meta-xylene)(meta-xylene) (para-xylene)(para-xylene)

In the IUPAC system, aromatic In the IUPAC system, aromatic compounds with one group attached compounds with one group attached to them are named by combining the to them are named by combining the name of the group with benzene.name of the group with benzene.

All these structures are named as All these structures are named as Chlorobenzene, and all represent the Chlorobenzene, and all represent the same compound.same compound.

There are three different ISOMERIC There are three different ISOMERIC compounds with two substituents on compounds with two substituents on the ring. The positions of the the ring. The positions of the substituents on these compounds are substituents on these compounds are indicated as follows:indicated as follows:

ortho (or 1, 2 - ) meta (1, 3 - )ortho (or 1, 2 - ) meta (1, 3 - ) para (or 1, 4 - para (or 1, 4 - ))

abbreviated o-abbreviated o- abbreviated m- abbreviated m-abbreviated p-abbreviated p-

Using benzene or toluene as parent Using benzene or toluene as parent structure, the following examples structure, the following examples illustrate the use of the systemillustrate the use of the system

o-dichlorobenzeneo-dichlorobenzene m-dichlorobenzenem-dichlorobenzene p- p-dichlorobenzenedichlorobenzene

o-chlorotolueneo-chlorotoluene m-chlorotoluenem-chlorotoluene p- p-chlorotoluenechlorotoluene

For compounds with three or more substituents For compounds with three or more substituents on the ring, we must use numbers to indicate on the ring, we must use numbers to indicate the position on the ring and apply the following the position on the ring and apply the following rules:rules:

1.1. The parent structure is benzene or tolueneThe parent structure is benzene or toluene2.2. For benzene, the group name written next to For benzene, the group name written next to

the word “benzene” becomes position the word “benzene” becomes position number 1 on the ring and the ring is number 1 on the ring and the ring is numbered in a direction that will give the numbered in a direction that will give the lowest possible numbers to the substituents.lowest possible numbers to the substituents.

3.3. For toluene, the methyl group becomes For toluene, the methyl group becomes position number 1 on the ring and the ring position number 1 on the ring and the ring is numbered in a direction that will give the is numbered in a direction that will give the lowest possible numbers to the substituents. lowest possible numbers to the substituents. The number 1 position is assumed in both The number 1 position is assumed in both benzene and toluene derivatives, but is not benzene and toluene derivatives, but is not indicated in the name.indicated in the name.

4.4. All groups are placed in alphabetical order All groups are placed in alphabetical order except the group in the number 1 position.except the group in the number 1 position.

ExamplesExamples(a)(a)

IodobenzeneIodobenzene

(b)(b)

m-dinitrobenzenem-dinitrobenzene

(c)(c)

p-nitrobromobenzene p-nitrobromobenzene

(d)(d)

4 – bromo – 2 - nitrotoluene4 – bromo – 2 - nitrotoluene

(e)(e)

2, 5 – dibromo – 3 nitrotoluene2, 5 – dibromo – 3 nitrotoluene

HydrocarbonsHydrocarbons

1. Benzene Series1. Benzene Series BenzeneBenzene C6H6C6H6 TolueneToluene C6H5 + CH3C6H5 + CH3 XyleneXylene C6H4 (CH3)2C6H4 (CH3)2 EthylbenzeneEthylbenzene C6H5 + C2H5C6H5 + C2H5

They :They : Are used extensively as solventsAre used extensively as solvents Are insoluble in water (relatively)Are insoluble in water (relatively) Are common constituents of petroleum Are common constituents of petroleum

productsproducts Cause cancers to humanCause cancers to human

Styrene is a benzene derivative used Styrene is a benzene derivative used in the production of polystyrene in the production of polystyrene productsproducts

StyreneStyrene

2. Polyring Hydrocarbons2. Polyring Hydrocarbons

(a) Naphthalene (C10 H8)(a) Naphthalene (C10 H8)

(b) Anthracene (C14 H10)(b) Anthracene (C14 H10)

((c) Phenanthrene (C14H10)c) Phenanthrene (C14H10)

Chlorinated Aromatic Chlorinated Aromatic HydrocarbonHydrocarbon

(1) Chlorinated Benzenes(1) Chlorinated BenzenesThey are benzene with one or more of the hydrogen are replaced They are benzene with one or more of the hydrogen are replaced by chlorineby chlorine

(2) Polychlorinated Biphenyls (PCBs)(2) Polychlorinated Biphenyls (PCBs)They are chlorinated benzenes with the following general They are chlorinated benzenes with the following general structure:structure:

X can be H or ClX can be H or Cl There are 209 possible PCBsThere are 209 possible PCBs Stable compounds (some can be biodegraded)Stable compounds (some can be biodegraded) Used widely as coolants in transformers, solvents, and Used widely as coolants in transformers, solvents, and

hydraulic fluidshydraulic fluids Bio-concentrateBio-concentrate

Derivatives of the Derivatives of the HydrocarbonsHydrocarbons

1. Organic Halides1. Organic Halides

ExamplesExamples DDT (dichlorodiphenyltrichloroethane)DDT (dichlorodiphenyltrichloroethane) Chlorofluorocarbons (CFC, CF2Cl2, CFCl3)Chlorofluorocarbons (CFC, CF2Cl2, CFCl3)

OrganicHalides

Alkyl halides

Alkyl group attached to a halogen atom such as F, Cl, Ba, I.

General formula:

R – X

R = alkyl groupX = halogen atom

Aryl halidesHalogen atom attached to an aromatic ring.

General formula:

Ar – X

Ar = Aromatic ringX = halogen atom

NomenclatureNomenclature

NomenclatureNomenclature

ExamplesExamples

Classifications of Classifications of AlcoholsAlcohols

Common AlcoholsCommon Alcohols

Chemical Reactions of Chemical Reactions of AlcoholsAlcohols

NomenclatureNomenclature

ExamplesExamples

NomenclatureNomenclature

ExamplesExamples

NomenclatureNomenclature

Trivial names of few aldehydes are Trivial names of few aldehydes are accepted by IUPAC system. These accepted by IUPAC system. These names are derived from the names are derived from the corresponding carboxylic acids by corresponding carboxylic acids by replacing the replacing the –ic–ic of the acid by of the acid by --aldehydealdehyde

ExamplesExamples

Common AldehydesCommon Aldehydes

NomenclatureNomenclature

(1) If both groups attached to the (1) If both groups attached to the carbonyl group are alkyl groups, they carbonyl group are alkyl groups, they are named as follows:are named as follows:

Name the alkyl groups attached to the Name the alkyl groups attached to the carbonyl group. If both groups are the carbonyl group. If both groups are the same, the prefix -di is usedsame, the prefix -di is used

Add the word “ketone”Add the word “ketone”

ExamplesExamples

to name compounds as phenones, the to name compounds as phenones, the follwing should be done:follwing should be done:

Name the cyl group as given aboveName the cyl group as given above Add phenone to the name of the acyl Add phenone to the name of the acyl

groupgroup

ExamplesExamples

ExampleExample

Ketones are prepared by oxidation of Ketones are prepared by oxidation of secondary alcoholsecondary alcohol

NomenclatureNomenclature

ExamplesExamples

NomenclatureNomenclature

(1) The systematic IUPAC of the acid (1) The systematic IUPAC of the acid is used.is used.

(2) Replace –ic by –ate.(2) Replace –ic by –ate.

ExamplesExamples

NomenclatureNomenclature

(1) when trivial names of carboxylic acids (1) when trivial names of carboxylic acids are used, the –ic acid part of the name is are used, the –ic acid part of the name is replaced by the ending –amide (i.e. the replaced by the ending –amide (i.e. the amide of acetic acid is acetamide)amide of acetic acid is acetamide)

(2) the IUPAC name is obtained by (2) the IUPAC name is obtained by dropping the –oic acid ending of the dropping the –oic acid ending of the IUPAC name of the acid and replacing it IUPAC name of the acid and replacing it with the ending –amide.with the ending –amide.

ExamplesExamples

NomenclatureNomenclature

ExamplesExamples

Cyclic Aliphatic Cyclic Aliphatic CompoundsCompounds

Heterocyclic CompoundsHeterocyclic Compounds

Food and Related Food and Related CompoundsCompounds

Fats, Oils and WaxesFats, Oils and Waxes

Proteins and Amino Proteins and Amino AcidsAcids

Fate of Organics (Table Fate of Organics (Table 5-14)5-14)