Alcohols, Phenols, Thiols, and Ethers
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Alcohols, Phenols, Thiols, and EthersChapter 13
IntroductionAlcohol organic compound that contains a hydroxyl (-OH) group attached to an alkyl groupPhenol organic compound that contains a hydroxyl (-OH) group attached to an aryl groupEther organic compound that has two alkyl or aryl groups attached to the oxygen atom; can be thought of as a substituted alcohol.
ExamplesAlcohols-OH hydroxyl CH3-OH CH3CH2-OH
Ethers -O- CH3-O-CH3
Practice Problem 1 Classify each as an alcohol (1), phenol (2), or an ether (3):
A. _____ CH3CH2-O-CH3C. _____ CH3CH2OH
Solution 1 Classify each as an alcohol (1), phenol (2), or an ether (3):
A. ____ CH3CH2-O-CH3C. ____ CH3CH2OH
B. _ __
Structure and PropertiesR-O-H portion of alcohol is similar to the structure of water.The oxygen and two atoms bonded to it lie in the same plane.The bond angle is 104Hydroxyl groups are very polar because of significantly different electronegativities.Hydrogen bonding can form between alcohol molecules.
Results of Hydrogen BondingAlcohols boil at much higher temperatures than hydrocarbons of similar molecular weight.Alcohols with fewer than five carbons are very soluble in water.Alcohols with five to eight carbons are moderately soluble in water.As the nonpolar (R) portion of the alcohol gets larger, the water solubility decreases.
Very large alcohols are not soluble in water.Hydrophobic water fearing; used to describe nonpolar region of moleculeHydrophilic water loving; used to describe polar region of molecule
CH3CH2CH2CH2CH2CH2CH2CH2CH2OHHydrophobicHydrophilicSolubility of Alcohols
Solubility of AlcoholsAn increase in the number of hydroxyl groups will increase the influence of the polar hydroxyl group.Diols and triols are more water soluble than alcohols with only a single hydroxyl group.
Practice Problem 2Circle the more soluble alcohol in each pair.
Solution 2Circle the more soluble alcohol in each pair.
Nomenclature of AlcoholsA carbon compound that contain -OH (hydroxyl) groupIn IUPAC name, the -e in alkane name is replaced with -ol.CH4 methaneCH3OH methanol (methyl alcohol)CH3CH3ethaneCH3CH2OH ethanol (ethyl alcohol)
More Names of AlcoholsIUPAC names for longer chains number the chain from the end nearest the -OH group.CH3CH2CH2OH OH CH3CHCH3 CH3 OH CH3CHCH2CH2CHCH3
Alcohols that contain more than one hydroxyl groupAlcohols containing two hydroxyl groups are named diols.Alcohols containing three hydroxyl groups are named triols.A number giving the position of each of the hydroxyl groups is needed in these cases.
Practice Problem 3
Name the following alcohols:A. OH
Name the following alcohols:A. OH CH3CHCHCH2CH3
HomeworkPages 379-380 13.11-13.14Page 360 13.1 13.2Due Tomorrow!!!!
Section 13.3It is your responsibility to read over section 13.3 Medically Important Alcohols (pgs. 360-361) and take notes on the material covered!It will be on the weekly quiz and the test!
Classification of AlcoholsAlcohols can be classified as primary (1), secondary (2), or tertiary (3) depending on the number of alkyl groups attached to the carbon bearing the OH group.Methanol 1 alcohol 2 alcohol 3 alcohol ethanol 2-propanol 2-methyl-2-propanol
Practice Problem 4Classify each of the following alcohols as primary, secondary, tertiary, or aromatic.
HomeworkPages 380-381: 13.15, 13.16, 13.18, 13.19, 13.20, 13.21, 13.22, 13.27, and 13.28Due Tomorrow!
Preparation of AlcoholsREVIEW: Hydration an addition reaction in which a water molecule is added to an alkene; requires acid as catalyst
Alkene Water Alcohol Markovnikovs rule applies!!
Preparation of AlcoholsHydrogenation of aldehydes and ketonesIn an aldehyde, R1 and R2 may be either alkyl groups or H. In a ketone, R1 and R2 are both alkyl groups.
We will discuss this in more detail in section 14.4.
Preparation of Alcohols YOU TRY THESE!+
Dehydration of AlcoholsAlcohols undergo dehydration (lose water) when heating with concentrated sulfuric or phosphoric acid. Dehydration is an example of an elimination reaction.Elimination reaction a reaction in which a molecule loses atoms or ions from its structure.Dehydration is opposite of hydration!
Dehydration of AlcoholsGeneral Reaction
Dehydration of AlcoholsZaitsevs rule in an elimination reaction, the alkene with the greatest number of alkyl groups on the double bonded carbon (more highly substituted alkene) is the major product of the reactionAnother example:
Oxidation ReactionsOxidation loss of electrons; add O and/or lose HReduction gain of electrons; add H and/or lose OCommon oxidizing agents:Basic potassium permanganate (KMnO4/OH-)Chromic Acid (H2CrO4)[O] Any general oxidizing agent
Oxidation of Primary AlcoholsGeneral equation:Primary alcohol aldehyde
Oxidation of Secondary AlcoholsGeneral equation:Secondary alcohol ketone OR-C-R EXAMPLE:2-propanol
Oxidation of Tertiary AlcoholsGeneral equation:Tertiary alcohol NO REACTION!!!
YOU TRY THESE!
PhenolsPhenols compounds in which the hydroxyl group is attached to a benzene ringThey are polar compounds because of the polar hydroxyl group.Smaller phenols are somewhat soluble in water.They are found in fragrances and flavorings and are also used as preservatives and germicides.
Common Phenols and their UsesThymol (mint)CH3OH(CH3)2HCCarvacrol (savory)
Common Phenols and their UsesButylated hydroxytoluene, BHT(Food preservative)Phenol(Carbolic acid when dissolved in water)Antiseptic and disinfectant used by Joseph Lister to bathe wounds and sterlize instruments
What are they?
How are they used?
What do you know about them?
Structure of EthersSimilar structure to alcohols
Alcohols: R-OHOH is hydroxy group
Ethers: R-OR OR is alkoxy group
Alkoxy groupR groups can be the same:
Both R groups have one carbon
R groups can be different:
One R group has three carbons while the other has one
Alkoxy groupThe root names are used with oxy to name that portion of the ether: meth- + -oxy eth- + -oxy prop- + -oxy
= methoxy= ethoxy= propoxy
Naming ethers IUPAC WayFind the root name of the smaller R group Ex: meth-, eth-, prop-Add oxy Ex: methoxy, ethoxy, propoxyAdd the full name of the larger R group EXAMPLE:
Name that ether
Draw the structure of:1. methoxypropane
Naming Ethers Common NameName by placing the names of the two alkyl groups attached to the ether oxygen as words in front of the word ether. Typically this is done in alphabetical order.Diethyl EtherEthyl methyl etherButyl propyl ether
Properties of ethersThe C-O bond in ethers is polar, making the molecule polar
Ethers have very low boiling points
Ethers are relatively inert, but flammable in air
Lets compareEtherCH3 O-CH2CH3
Molecular Formula:C3H8OMolecular Weight: 60.09g/molBoiling Point:7.9CAlcoholCH3CH2CH2-OH
Molecular Formula:C3H8OMolecular Weight:60.09g/molBoiling Point:97.2C
Preparing ethersEthers are formed from alcohols
R-OH + R-OH R-O-R +H2O
R and R can be the same or differentCalled a dehydration reactionH+
Predict the products
Common usesEthers as anesthetics: Penthrane Enthrane
Ethers as additives in gasoline MTBE methyl tert-butyl ether
ThiolsCompounds that contain the sulfhydryl group (-SH)Similar to alcohols in structure, but the sulfur atom replaces the oxygen atomHave nauseating aromas defense spray of North American striped skunkTrans-2-butene-1-thiol
Naming ThiolsUse the same rules as for alcohols except that the full name of the alkane is retained.Add the suffix thiol.ethanethiol3-methyl-1-butanethiol1,2-ethanedithiol
Uses of ThiolsThiols are involved in protein structure and conformation.Cysteine is an amino acid that contains a sulfhydryl group. BAL (British Anti-Lewisite) is used as an antidote for mercury poisoning.Coenzyme A serves as a carrier of acetyl groups in biochemical reactions.
HomeworkPg. 381-382: 13.43, 13.44, 13.45, 13.48, 13.49, 13.51, 13.52, 13.53, 13.59, 13.60