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Alcohols, Phenols, and Thiols • An alcohol contains a hydroxyl group (–OH) attached to a carbon chain. • A phenol contains a hydroxyl group (–OH) attached to a benzene ring. • A thiol contains a thiol group (–SH) attached to a carbon chain. 1 Guide to Naming Alcohols 2 Naming Alcohols The names of alcohols • in the IUPAC system, replace -e of the alkane name with -ol. • that are common names, use the name of the alkyl group followed by alcohol. Formula CH4 IUPAC Methane Common Name CH3─OH Methanol Methyl alcohol CH3─CH3 Ethane CH3─CH2─OH Ethanol Ethyl alcohol 3 Naming Alcohols When an alcohol contains a chain with three or more carbon atoms, the chain is numbered to give the position of the −OH group and any substituents on the chain. Formula CH3─CH2─CH2─OH IUPAC Common Name 1-Propanol Propyl alcohol 2-Propanol Isopropyl alcohol OH CH3─CH─CH3 4 Naming Alcohols In IUPAC names for longer carbon chains, the chain is numbered from the end nearer the –OH group. 5 Naming Alcohols We can also draw skeletal structures for alcohols. CH3─CH2─CH2─OH OH CH3─CH─CH2─CH3 OH OH 1-Propanol 2-Butanol 6 Some Typical Alcohols Rubbing alcohol: 2-Propanol (isopropyl alcohol) Antifreeze: 1,2-Ethanediol (ethylene glycol) Glycerol: 1,2,3-Propanetriol © 2013 Pearson Education, Inc. Chapter 11, Section 4 7 Learning Check Give the IUPAC name for each of the following. A. CH3—CH2—CH2—CH2—OH B. © 2013 Pearson Education, Inc. Chapter 11, Section 4 8 Learning Check Give the IUPAC name for each of the following. Step 1 Name the longest carbon chain attached to the −OH group by replacing the -e in the corresponding alkane name with -ol . A. CH3—CH2—CH2—CH2—OH butanol pentanol B. © 2013 Pearson Education, Inc. Chapter 11, Section 4 9 Learning Check Give the IUPAC name for each of the following. Step 2 Number the chain starting at the end closer to the −OH group. A. CH3—CH2—CH2—CH2—OH 4 3 2 1 butanol B. pentanol 1 © 2013 Pearson Education, Inc. 2 3 4 5 Chapter 11, Section 4 10 Learning Check Give the IUPAC name for each of the following. Step 3 Give the location and name of each substituent relative to the −OH group. A. CH3—CH2—CH2—CH2—OH 4 3 2 1 butanol B. 3-methyl-1-pentanol 1 © 2013 Pearson Education, Inc. 2 3 4 5 Chapter 11, Section 4 11 Learning Check Draw the condensed structural formula of the following. A. 3-Pentanol B. Propanol C. 3-Methylcyclohexanol 12 Solution Draw the condensed structural formula of the following. A. 3-Pentanol B. Propanol CH3—CH2—CH2—OH C. 3-Methylcyclohexanol OH CH3 © 2013 Pearson Education, Inc. Chapter 11, Section 4 13 Phenol Phenol • is the IUPAC name for benzene with a hydroxyl group. • is used in antiseptics and disinfectants. Phenol © 2013 Pearson Education, Inc. Chapter 11, Section 4 14 Naming Phenols To name a phenol with two substituents, • assign C-1 to the carbon attached to the –OH. • number the ring to give the substituents the lowest numbers. Phenol © 2013 Pearson Education, Inc. 3-chlorophenol Chapter 11, Section 5 3-methylphenol 15 Learning Check Name the following phenol. OH Cl © 2013 Pearson Education, Inc. Chapter 11, Section 5 16 Solution Name the following phenol. Step 1 Name an aromatic alcohol as a phenol. -phenol OH 1 2 Step 2 Number the chain starting 3 at the end closer to the −OH group. (In phenol, carbon number one is the −OH group.) Step 3 Give the location and name of each substituent relative to the −OH group. 3-Chloro-phenol © 2013 Pearson Education, Inc. Chapter 11, Section 5 Cl 17 Derivatives of Phenol Compounds of phenol are the active ingredients in the essential oils of cloves, vanilla, nutmeg, and mint. 18 Thiols Thiols • are organic compounds that contain a –SH group. • are named in the IUPAC system by adding thiol to the alkane name of the longest carbon chain. 19 Naming Thiols In thiols with long carbon chains, the chain is numbered to give the −SH group the lowest possible number. 20 Sources of Thiols Thiols • often have strong odors. • are used to detect gas leaks. • are found in onions, oysters, and garlic. 21 Ethers • Ethers consist of an oxygen atom that is connected by single bonds to two carbon groups (alkyl or aromatic). • Simple ethers are named by listing the alkyl names in alphabetical order followed by ether CH3─O─CH3 methyl © 2013 Pearson Education, Inc. CH3─CH2─O─CH3 methyl ethyl Chapter 11, Section 4 methyl 22 Ethers as Anesthetics Early anesthetics, such as diethyl ether CH3─CH2─O─CH2─CH3, • worked by inhibiting pain signals to the brain. • caused nausea and were flammable. 23 Cyclic Ethers A cyclic ether • contains an O atom in a carbon ring. • is called a heterocyclic compound. • typically has 5 (furan) or 6 atoms (pyran) in the ring. O O O O O Furan Tetrahydrofuran Pyran 1,4-Dioxane © 2013 Pearson Education, Inc. Chapter 11, Section 5 24 Classifying Alcohols Alcohols can be classified as • primary (1), which has one alkyl group attached to the carbon with the −OH group, • secondary (2), which has two alkyl groups attached to the carbon with the −OH group, or • tertiary (3), which has three alkyl groups attached to the carbon with the −OH group. 25 Classifying Alcohols 26 Learning Check Classify each of the following alcohols as primary, secondary, or tertiary. A. 2-propanol B. 1-butanol OH C. OH D. 27 Solution Classify each of the following alcohols as primary, secondary, or tertiary. A. 2-propanol secondary B. 1-butanol primary OH C. tertiary OH D. secondary 28 Boiling Points of Alcohols Alcohols • form hydrogen bonds between alcohol molecules. • have higher boiling points than alkanes and ethers of similar mass. 29 Boiling Points of Ethers Ethers • have an O atom, but no H is attached. • cannot form hydrogen bonds between ether molecules. • have boiling points similar to alkanes of similar mass. 30 Solubility of Alcohols and Ethers in Water Alcohols and ethers are more soluble in water than are alkanes because the oxygen atom can form hydrogen bonds with water. Alcohol Solubility in H2O 1–3 carbon atoms completely soluble 4 carbon atoms slightly soluble 5 or more carbon atoms insoluble Ethers containing up to 4 carbon atoms are slightly soluble in water. 31 Solubility of Alcohols and Ethers in Water 32 Combustion of Alcohols Combustion is the reaction of an alcohol with O2 to produce CO2, H2O and energy. © 2013 Pearson Education, Inc. Chapter 11, Section 4 33 Dehydration of Alcohols Dehydration of an alcohol occurs • when heated with an acid catalyst, H+ • with the loss of –H and –OH from adjacent carbon atoms to form water alcohol alkene 34 Saytzeff’s Rule According to Saytzeff’s rule, the dehydration of a secondary alcohol favors the product in which hydrogen is removed from the carbon atom in the chain with the smaller number of H atoms 35 Learning Check Write the equations for the reactions when 2propanol undergoes _______. A. combustion B. dehydration 36 Solution Write the equations for the reactions when 2-propanol undergoes _______. A. combustion B. dehydration 37 Formation of Ethers Ethers form when dehydration occurs at lower temperatures, (130 C) in the presence of an acid catalyst. two methanol molecules dimethyl ether 38 Oxidation and Reduction In the oxidation of an organic compound, • there is an increase in the number of C–O bonds. • there is a loss of H. In the reduction of an organic compound, • there is a decrease in the number of C–O bonds. • there is a gain of H. 39 Oxidation and Reduction An alcohol is more oxidized than an alkane; an aldehyde or ketone is more oxidized than an alcohol; a carboxylic acid is more oxidized than an aldehyde. 40 Oxidation of Primary (1) Alcohols Primary alcohols are oxidized to form aldheydes. Ethanol (ethyl alcohol) Ethanal (acetaldehyde) 41 Oxidation of Secondary (2) Alcohols Secondary alcohols are oxidized to form ketones. 2-Propanol (isopropyl alcohol) 2-Propanone(dimethyl ketone, “acetone”) 42 Oxidation of Tertiary (3) Alcohols Tertiary alcohols do not readily oxidize. There is no H on the C–OH to oxidize. 2-Methyl-2-propanol 43 Oxidation of Ethanol in the Body In the body, • ethanol is oxidized by enzymes in the liver. • aldehyde product impairs coordination. 44 Learning Check Select the product from the oxidation of _______. Solution Select the product from the oxidation of _______. Answer is B. 46