Structure and Nomenclature of Alcohols and Phenols

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Alcohols and phenols are organic compounds with distinct functional groups. Alcohols have a hydroxyl group attached to an alkyl group, while phenols have the hydroxyl function directly attached to a benzene ring. Learn about the classification, nomenclature, and properties of alcohols along with their chemical reactions and preparation methods.

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Alcohols and Phenols 1435 1435- -1436 2014 2014- -2015 1436 2015 1

Alcohols and Phenols Learning Objectives Chapter six concerns alcohols and phenols and by the end of this chapter the student will: know the difference in structure between alcohols and phenols Know the different classes of alcohols Know how to name alcohols and phenols Know the physical properties (solubility, boiling and melting points) Know how hydrogen bonds are formed and its effect on boiling points of alcohols Know the acidic properties of alcohols and phenols know the different methods that can be used to prepare alcohols and phenols. Know the chemical reactions of these compounds ( some reactions are review, others are extensions of the chemistry that will be discussed on chapters 8, 9 & 10 145 Chem.

Alcohols and Phenols Structure Of Alcohols and Phenols Alcohols and phenols may be viewed as organic derivatives of water. H-O-H R-O-H or PhCH2OH Ph-O-H Water Alcohol Phenol Alcohols and phenols have a common functional group, the hydroxyl group, OH. - In alcohols the hydroxyl group is attached to an alkyl group, R. - In phenols the hydroxyl function is directly attached to benzene ring OH OH OH Cyclohexanol Phenol Benzyl alcohol 145 Chem. 3

Alcohols and Phenols Classification and Nomenclature of Alcohols Alcohols are classified according to the type of the carbon atom connected to the hydroxyl group (carbinol carbon) into: 145 Chem. 4

Alcohols and Phenols NOMENCLATURE OF ALCOHOLS IUPAC Nomenclature Of Alcohols Alcohols are named according to the following rules: 1. Select the longest continuous carbon chain that contains the -OH group. Replace the ending e of the alkane by the suffix ol 2. If a molecule contains both an -OH group and a C=C or c c bond; Choose the chain that include both of them even if this is not the longest chain. The name should include suffixes indicate presence of both the OH group and the unsaturated groups. The OH group takes precedence over the double or triple bonds in getting the lower number. Cyclic alcohols are named using the prefix cyclo-, the carbon bearing the hydroxyl group is assumed to take number 1. 3. The suffix diol is added to the name of the parent hydrocarbon when there are two OH groups. 4. The suffix triol is added when there are three OH groups. 145 Chem. 5

Alcohols and Phenols Common Nomenclature Of Alcohols List the names of alkyl substituents attached to the hydroxyl group, followed by the word alcohol. If two OH groups present on two adjacent carbons these known as glycols Primary alcohols CH3OH CH3CH2OH CH2=CHCH2OH Allyl alcohol Common Methyl alcohol Ethyl alcohol 2-Propen-1-ol IUPAC Methanol Ethanol 145 Chem. 6

Alcohols and Phenols Secondary and tertiary alcohols OH CH3 OH OH Common Isopropyl alcohol Cyclopentyl alcohol Methylcyclohexyl alcohol 1-Methyl-1-cyclohexanol IUPAC 2-Propanol Cyclopentanol 145 Chem. 7

Alcohols and Phenols Examples OH OH OH 1-Phenylmethanol Benzyl alcohol (common name) 2-Phenylethanol 4-Methyl-2-cyclohexen-1-ol OH 5 2 3 4 1 Cl (CH3)2C=CHCH(OH)CH3 4- Methyl-3-penten-2-ol OH OH 4-Chloro-2-methyl-1-penten-3-ol Ethan-1,2-diol Ethylene glycol (common name) 145 Chem. 8

Alcohols and Phenols Examples OH OH OH 5-Ethyl-hex-5-en-3-ol But-3-en-2-ol Pent-4-yn-1-ol OH OH CH3 HO OH OH OH OH Propane-1,2,3-triol or 1,2,3,-Propantriol Propane-1,2-diol or 1,2-Propanediol IUPAC Ethane-1,2-diol 145 Chem. Common Ethylene glycol Glycerol or Glycerin Propylene glycol

Alcohols and Phenols Physical Properties of Alcohols 1) Boiling Points of Alcohols The boiling points increase with increase in molecular weights. Alcohols have higher boiling points(b .p.) than alkanes of similar weight this is due to the presence of hydrogen bonds between molecules of alcohols. hydrogen bond Br> > > > OH OH OH Melting & boiling points Increases in this direction 145 Chem. 10

Alcohols and Phenols 2) Solubility Of Alcohols and Phenols Alcohol and water contain hydroxyl group that can form hydrogen bonds. The hydroxyl group is hydrophilic water loving The alkyl group of alcohols is hydrophobic water hating As the number of the OH group in alcohol increases, the solubility in water increases. Diols and triols are more soluble in water than monohydroxyalcohols. The lower alcohols are completely miscible with water As the number of carbons in the alcohol increases, the solubility in water decreases. Homework H C IUPAC H2C CH2 Nomenclature OH OH OH Commen 145 Chem. 11

Alcohols and Phenols 3) Acidic Properties of Alcohols: Alcohols are very weak acids The hydroxyl proton of an alcohol is weakly acidic A strong base can abstract the hydroxyl proton to give an alkoxide ion. B +B-H R-O-H R-O ClCH2CH2OH CH3CH2OH CH3OH PKa= 15.9 15.5 15.3 less acidic most acidic Electron-withdrawing group (-I) increase acidity Electron-releasing group (+I) decrease acidity Cl Cl H3CO Cl > > > OH OH OH OH Cl 12 145 Chem.

Alcohols and Phenols Synthesis (Preparation) of Alcohols 1- Hydration From Alkenes H3O+ OH + OH major minor 1- Oxidation of Alkenes OH KMnO4 OH-/H2O OH 2- From alkyl halide cis glycol alcohol,KOH (elimination of HX using base gives alkene) H3C C CH2 heat H CH3CH2CH2Cl dil OH- nucleophilic substitution CH3CH2CH2OH or aq. KOH 145 Chem. 13

Alcohols and Phenols 3- Reduction of aldehydes, ketones and carboxylic acids O H C CH3 OH LiAlH4 or NaBH4 or H2/Pt H3C CH3CCH3 O H2 C OH LiAlH4 CH3COH H3C 145 Chem. 14

Alcohols and Phenols 4- Addition of Grignard compounds to aldehydes & ketones OH C CH3 OMgCl C CH3 MgCl H3C H3C O H3O+ + Tertiary alcohol CH3CCH3 Ketone Secondary alcohol l Primary alcohol Methanal formaldehyde 145 Chem. 15

Alcohols and Phenols Reaction of Alcohols 1. Dissociation of O-H Bond Reaction as acids (Breaking of oxygen- Hydrogen bond CO H) A. Formation of Salt (Alkoxide formation) H2 C ONa Sodium ethoxide Na CH3CH2OH H3C B. Formation of Esters H+ H+/ H2O 145 Chem. 16

Alcohols and Phenols 2. Dissociation of C-O Bond Reaction with C OH bond cleavage A. Elimination Reactions conc.H2SO4 CH3CH2OH H2C CH2 B. Substitution Reaction HCl/ ZnCl2 H3C CH2Cl CH3CH2OH or SOCl2 or PCl3 or PCl5 145 Chem. 17

Alcohols and Phenols C. Oxidation Reactions O Cu / CH3CH2OH H3C CH or PCC O KMnO4 CH3CH2OH H3C C-OH OH O Cu / CH3CHCH3 H3C C-CH3 or KMnO4 or PCC Pridinium Chloro chromate , CrO3. HCl PCC = N 145 Chem 18

Alcohols and Phenols Nomenclature and acidity of Phenols Phenols (compounds having hydroxyl group directly attached to a benzene ring ) are generally named as derivatives of the simplest member of the family, phenol Acidity : Alcohols and phenols have weak acidic properties. Phenols are much stronger acids than alcohols. Introduction of electron-withdrawing groups, such as NO2 or CN, on the ring increases the acidity of phenols. 145 Chem. 19

Alcohols and Phenols OH OH OH OH OH O2N O2N NO2 < < < < NO2 NO2 NO2 CH3 Picric acid 2,4,6-Trinitrophenol PH=0.25 4-Methylphenol p-Cresol (Common) PH>10 Phenol 2,4-Dinitrophenol 4-Nitrophenol PH=4 PH=10 PH=7 OH OH OH CHO COOH Cl NH2 2-Hydroxybenzoic acid o-Hydroxybenzoic acid Salicylic acid 2-Hydroxybenzaldehyde o-Hydroxybenzaldehyde Salicylaldehyde 3-Amino-5-chlorophenol 145 Chem. 20

Alcohols and Phenols Synthesis of Phenols 145 Chem. 21

Alcohols and Phenols Reactions Phenols Ethers formation O CrO3 / H+ O p-Benzoquinone 145 Chem. 22

Alcohols and Phenols 2. Electrophilic Substitution Reactions 145 Chem. 23

Alcohols and Phenols Home Work KMnO4 OH-/H2O MgCl O H3O+ + HCH O MgBr H2C H3O+ + 145 Chem. 24

Alcohols and Phenols 4) The IUPAC name of is: A) 4-Ethyl-5-heptyn-3-ol B) 4-Ethyl-5-heptan-3-ol C) 4-Ethyl-5-hepten-3-ol D) 4-Etyl-2-hepten-5-ol 5) The IUPAC name of is: A) 3-Methyl-1-bromocyclohexanol B) 2-Bromo-3-methylcyclohexanol C) 4-Bromo-2-methylcyclohexanol D) 3-Bromo-1-methylcyclohxanol OH 6) The most acidic compound is: 145 Chem. 25

Alcohols and Phenols 7) The common name of 2-methyl-2-propanol is: A) Allyl alcohol B) Isopropyl alcohol C) tert-Butyl alcohol D) Benzyl alcohol 8) The following reaction gives A) 4-Ethylphenol B) 2-Ethylphenol C) Ethylphenyl ether D) Ethylphenyl ketone 145 Chem. 26

Alcohols and Phenols 9) The major product for the following reaction is 10) The product of the reaction shown below is 11) Which of the following compounds has the highest boiling point?