Organic Chemistry Fourth Edition David Klein Chapter 12 Alcohols and Phenols This deck contains equations authored in Math Type For the full experience please download the Math Type software plug in Copyright 2021 John Wiley Sons Inc 12 1 Alcohols and Phenols Alcohols Overview Alcohols possess a hydroxyl group OH Hydroxyl groups are extremely common in natural compounds Copyright 2021 John Wiley Sons Inc 2 12 1 Alcohols and Phenols Alcohols in Natural Compounds Hydroxyl groups in natural compounds Copyright 2021 John Wiley Sons Inc 3 12 1 Alcohols and Phenols Phenols in Natural Compounds Phenols possess a hydroxyl group directly attached to a benzene ring Copyright 2021 John Wiley Sons Inc 4 12 1 Alcohol Nomenclature Overview Alcohols are named using the same procedure we used in Chapter 4 to name alkanes with minor modifications 1 Identify the parent chain which should include the carbon that the OH is attached to 2 Identify and name the substituents 3 Assign a locant and prefix if necessary to each substituent Give the carbon that the OH is attached to the lowest number possible 4 List the numbered substituents before the parent name in alphabetical order Ignore prefixes except iso when ordering alphabetically 5 The OH locant is placed either just before the parent name or just before the ol suffix Copyright 2021 John Wiley Sons Inc 5 12 1 Alcohol Nomenclature Step One Alcohols are named using the same procedure we used in Chapter 4 to name alkanes with minor modifications 1 Identify the parent chain Copyright 2021 John Wiley Sons Inc 6 12 1 Alcohol Nomenclature Step Three Alcohols are named using the same procedure we used in Chapter 4 to name alkanes with minor modifications 3 Assign a locant and prefix if necessary to each substituent Give the carbon that the OH is attached to the lowest number Copyright 2021 John Wiley Sons Inc 7 12 1 Alcohol Nomenclature Step Five Alcohols are named using the same procedure we used in Chapter 4 to name alkanes with minor modifications 5 The OH locant is placed either just before the parent name or just before the ol suffix Copyright 2021 John Wiley Sons Inc 8 12 1 Alcohol Nomenclature Cyclic Alcohols For cyclic alcohols the OH group is always carbon 1 Common names for some alcohols are also frequently used Copyright 2021 John Wiley Sons Inc 9 12 1 Alcohol Nomenclature Type of Carbon Like halides alcohols are often classified by the type of carbon they are attached to Copyright 2021 John Wiley Sons Inc 10 12 1 Alcohol Nomenclature Phenols When an OH group is attached to a benzene ring the parent name is phenol Practice with SkillBuilder 12 1 Naming an Alcohol Copyright 2021 John Wiley Sons Inc 11 12 1 Commercially Important Alcohols Methanol Methanol CH3OH is the simplest alcohol With a suitable catalyst about 2 billion gallons of methanol is made industrially from CO2 and H2 every year Methanol is poisonous but it has many uses 1 Solvent 3 Fuel 2 Precursor for chemical syntheses Copyright 2021 John Wiley Sons Inc 12 12 1 Commercially Important Alcohols Ethanol Ethanol CH3CH2OH produced by fermentation of grains or fruits Industrially ethanol is made via acid catalyzed hydration of ethylene 5 billion gallons year in the U S alone Ethanol has many uses 1 Solvent precursor for chemical syntheses fuel Is denatured 2 Human consumption ethanol suitable for drinking and is to avoid heavy taxes heavily taxed Copyright 2021 John Wiley Sons Inc 13 12 1 Commercially Important Alcohols Isopropanol Isopropanol CH3CH OH CH3 a k a rubbing alcohol Isopropanol is made industrially from the acid catalyzed hydration of propylene Isopropanol is poisonous but it has many uses 1 Industrial solvent 2 Antiseptic 3 Gasoline additive Copyright 2021 John Wiley Sons Inc 14 12 1 Physical Properties of Alcohols Boiling Point The OH of an alcohol has a big effect on its physical properties Compare the boiling points below Alcohols have much higher BPs due to H bonding Copyright 2021 John Wiley Sons Inc 15 12 1 Physical Properties of Alcohols Miscibility in Water Alcohols with 3 carbons or less are miscible in water Alcohols with large carbon chains do not readily mix with water Copyright 2021 John Wiley Sons Inc 16 12 1 Physical Properties of Alcohols Anti Bacterial Properties An alcohol s potency as an anti bacterial agent depends on the size of the hydrophobic group The alcohol needs some water solubility to travel through aqueous media To kill a bacterium the alcohol should have a significant hydrophobic region to penetrate microbial membranes Copyright 2021 John Wiley Sons Inc 17 12 1 Physical Properties of Alcohols Hexylresorcinol Hexylresorcinol is used as an antibacterial and as an antifungal agent It has a good combination of hydrophobic and hydrophilic regions Practice with CONCEPTUAL CHECKPOINT 12 3 Copyright 2021 John Wiley Sons Inc 18 12 2 Acidity of Alcohols and Phenols Alkoxides A strong base is necessary to deprotonate an alcohol NaH is often used to generate the corresponding alkoxide Na K or Li metal is often used as well Practice with CONCEPTUAL CHECKPOINT 12 4 Copyright 2021 John Wiley Sons Inc 19 12 2 Acidity of Alcohols and Phenols ARIO Alkoxide conjugate base of an alcohol Remember ARIO to rationalize the relative acidity of an alcohol Copyright 2021 John Wiley Sons Inc 20 12 2 Acidity of Alcohols and Phenols Resonance Recall the factors that affect the acidity of alcohols and phenols 1 Resonance phenol is millions of times more acidic because the conjugate base phenoxide is resonance stabilized Copyright 2021 John Wiley Sons Inc 21 12 2 Acidity of Alcohols and Phenols Induction Recall the factors that affect the acidity of alcohols and phenols 2 Induction presence of electron withdrawing groups increases the acidity of an alcohol or phenol Copyright 2021 John Wiley Sons Inc 22 12 2 Acidity of Alcohols and Phenols Solvation Recall the factors that affect the acidity of alcohols and phenols 3 Solvation Effects The more poorly solvated a conjugate base the less stable it is and the less acidic its conjugate acid The conjugate base of tert butanol is less stable due to solvation effects Copyright 2021 John Wiley Sons Inc 23 12 2 Acidity of Alcohols and Phenols Sterics The tert butoxide ion is sterically hindered and not well solvated Practice with SkillBuilder 12 2 Comparing Acidity Copyright 2021 John Wiley Sons Inc 24 12 3 Preparation of Alcohols From RX Alcohols can be synthesized from alkyl halides via substitution The substitution occurs by SN1