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1 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. King Saud University Chemistry Department Structure Of Alcohols and Phenols Alcohols and phenols may be viewed as organic derivatives of water. H-O-H Water R-O-H or PhCH2OH Alcohol Ph-O-H 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 145 Chem. Phenol Benzyl alcohol Cyclohexanol 3 King Saud University Chemistry Department 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 King Saud University Chemistry Department 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 cΞc 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. 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 King Saud University Chemistry Department 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 Common Methyl alcohol Ethyl alcohol IUPAC Methanol Ethanol 145 Chem. CH2=CHCH2OH Allyl alcohol 2-Propen-1-ol 6 King Saud University Chemistry Department Secondary and tertiary alcohols OH OH CH3 OH Common Isopropyl alcohol IUPAC 145 Chem. 2-Propanol Cyclopentyl alcohol Cyclopentanol Methylcyclohexyl alcohol 1-Methyl-1-cyclohexanol 7 King Saud University Chemistry Department OH Examples OH OH 1-Phenylmethanol Benzyl alcohol (common name) 2-Phenylethanol OH Cl 4-Methyl-2-cyclohexen-1-ol OH OH Ethan-1,2-diol Ethelene glycol (common name) 4-Chloro-2-methyl-1-penten-3-ol 5 4 3 2 1 (CH3)2C=CHCH(OH)CH3 4- Methyl-3-penten-2-ol 145 Chem. 8 King Saud University Chemistry Department Examples OH OH OH But-3-en-2-ol 5-Ethyl-hex-5-en-3-ol Pent-4-yn-1-ol OH OH CH3 HO 145 Chem. OH OH IUPAC Ethane-1,2-diol Propane-1,2-diol or 1,2-Propanediol Common Ethylene glycol Propylene glycol OH OH Propane-1,2,3-triol or 1,2,3,-Propantriol Glycerol or Glycerin King Saud University Chemistry Department Physical Properties of Alcohols 1) Solubility Of Alcohols and Phenols Diols and triols are more soluble in water than monohydroxyalcohols. As the number of carbons in the alcohol increases, the solubility in water decreases. 2) Boiling Points of Alcohols The boiling points increase with increase in molecular weights. OH > OH > OH 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 145 Chem. 10 King Saud University Chemistry Department OH > OH > OH > Br > Melting & boiling points Increases in this direction H2C H C CH2 OH OH Homework IUPAC Nomenclature OH Commen 3) Acidic Properties of Alcohols Alcohols are very weak acids 145 Chem. 11 King Saud University Chemistry Department Synthesis (Preparation) of Alcohols 1- From Alkenes H3O+ OH + major minor OH OH KMnO4 OH-/H2O OH cis glycol 2- From alkyl halide alcohol,KOH heat H3C C CH2 H (elimination of HX using base gives alkene) CH3CH2CH2Cl dil OH- CH3CH2CH2OH 145 Chem. nucleophilic substitution 12 King Saud University Chemistry Department 3- Reduction of aldehydes, ketones and carboxylic acids O H LiAlH4 H C C CH3 3 CH3CCH3 or NaBH 4 OH or H2/Pt O CH MgBr H 3 H3C C CH3 CH3CH OMgBr O LiAlH4 CH3COH 145 Chem. H3O+ H H3C C CH3 OH H2 H3C C OH 13 King Saud University Chemistry Department 4Addition ketones MgCl O CH3CCH3 + of Grignard compounds to aldehydes & OH H3C C CH3 OMgBr H3C C CH3 H3O+ Tertiary alcohol Ketone Secondary alcohol Primary alcohol Methanal formaldehyde 145 Chem. 14 King Saud University Chemistry Department Reaction of Alcohols 1. Dissociation of O-H Bond Reaction as acids (Breaking of oxygen- Hydrogen bond CO ـــــH) A. Formation of Salt CH3CH2OH Na H2 H3C C ONa Sodium ethoxide B. Formation of Esters H+ H+/ H2O 145 Chem. 15 King Saud University Chemistry Department 2. Dissociation of C-O Bond Reaction with CــــOH bond cleavage A. Elimination Reactions CH3CH2OH conc.H2SO4 H2C CH2 B. Substitution Reaction CH3CH2OH HCl/ ZnCl2 H3C CH2Cl or SOCl2 or PCl3 or PCl5 145 Chem. 16 King Saud University Chemistry Department C. Oxidation Reactions CH3CH2OH OH CH3CHCH3 Cu/ or CrO3 Cu/ or CrO3 KMnO4 O H3C CH O H3C C-CH3 or PCC , CrO3. HCl PCC = Pridinium Chloro chromate N 145 Chem 17 King Saud University Chemistry Department 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. 18 King Saud University Chemistry Department 145 Chem. 19 King Saud University Chemistry Department Synthesis of Phenols 145 Chem. 20 King Saud University Chemistry Department Reactions Phenols Ethers formation O OH CrO3 / H+ OH Hydroquinone 145 Chem. O p-Benzoquinone 21 King Saud University Chemistry Department 2. Electrophilic Substitution Reactions 145 Chem. 22 King Saud University Chemistry Department Home Work KMnO4 OH-/H2O MgCl O HCH + O 145 Chem. H3O+ H2C MgBr H3O+ + 23 King Saud University Chemistry Department 4) The IUPAC name of 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: OH is: A) 3-Methyl-1-bromocyclohexanol B) 2-Bromo-3-methylcyclohexanol C) 4-Bromo-2-methylcyclohexanol D) 3-Bromo-1-methylcyclohxanol 6) The most acidic compound is: 145 Chem. 24 King Saud University Chemistry Department 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. 25 King Saud University Chemistry Department 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? Questions?