Saturated Hydrocarbons Section 20.1 Steven S. Zumdahl Susan A. Zumdahl Donald J. DeCoste Gretchen M. Adams University of Illinois at Urbana-Champaign Chapter 20 Organic Chemistry

Saturated Hydrocarbons Section To understand the types of bonds formed by the carbon atom 2.To learn about the alkanes 3.To learn about structural isomers 4.To learn to draw structural formulas 5.To learn to name alkanes and substituted alkanes 6.To learn about the composition and uses of petroleum 7.To learn about the chemical reactions of alkanes Objectives

Saturated Hydrocarbons Section 20.1 Carbon Chemistry Carbon is unusual.  Bonds strongly to itself  Forms long chains or rings Biomolecule – molecule that functions in maintaining and reproducing life Organic compounds – vast majority of carbon compounds  Exceptions – oxides and carbonates

Saturated Hydrocarbons Section 20.1 A. Carbon Bonding When carbon has 4 atoms bound to it, these atoms have a tetrahedral shape.

Saturated Hydrocarbons Section 20.1 A. Carbon Bonding Double bond Triple bond Sharing of 3 pairs of electrons Sharing of 2 pairs of electrons

Saturated Hydrocarbons Section 20.1 B. Alkanes Hydrocarbons – compounds composed of carbon and hydrogen  Saturated – all carbon-carbon bonds are single bonds  Unsaturated – containing carbon-carbon multiple bonds

Saturated Hydrocarbons Section 20.1 B. Alkanes Alkanes – saturated hydrocarbons

Saturated Hydrocarbons Section 20.1 B. Alkanes Normal, straight-chain or unbranched hydrocarbons Contain strings or chains of carbon atoms  Representations

Saturated Hydrocarbons Section 20.1 B. Alkanes

Saturated Hydrocarbons Section 20.1 C. Structural Formulas and Isomerism Structural isomerism – occurs when 2 molecules have the same atoms but different bonds

Saturated Hydrocarbons Section 20.1 D. Naming Alkanes The name for an alkane is based on Greek root with the suffix –ane. Basic principles

Saturated Hydrocarbons Section 20.1 D. Naming Alkanes For branched hydrocarbons use the longest continuous chain for the root name. Basic principles

Saturated Hydrocarbons Section 20.1 D. Naming Alkanes Alkanes missing one H atom can have another hydrocarbon attached at the missing H point. Basic principles

Saturated Hydrocarbons Section 20.1 D. Naming Alkanes Specify the names of substituents by numbering the C atoms starting at the end closest to the branching. Basic principles

Saturated Hydrocarbons Section 20.1 D. Naming Alkanes Basic principles

Saturated Hydrocarbons Section 20.1 D. Naming Alkanes If a substituent occurs more than once, use a prefix to show this. Basic principles 2,3-dimethylpentane

Saturated Hydrocarbons Section 20.1 D. Naming Alkanes

Saturated Hydrocarbons Section 20.1 Exercise Name each of the following: a) 2,2,4,5-tetramethylhexane b) 3,6-diethyl-3-methyloctane

Saturated Hydrocarbons Section 20.1 E. Petroleum Hydrocarbons are an energy resource.

Saturated Hydrocarbons Section 20.1 E. Petroleum Petroleum – thick, dark liquid composed mostly of hydrocarbon compounds Natural gas – consists mostly of methane, usually associated with petroleum deposits

Saturated Hydrocarbons Section 20.1 F. Reactions of Alkanes Combustion – reaction with oxygen Substitution – one or more H atoms are replaced with different atoms

Saturated Hydrocarbons Section 20.1 F. Reactions of Alkanes Dehydrogenation – one or more H atoms are removed and the product is an unsaturated hydrocarbon

Section 20.2 Unsaturated Hydrocarbons 1.To learn to name hydrocarbons with double and triple bonds 2.To understand addition reactions 3.To learn about the aromatic hydrocarbons 4.To learn to name aromatic compounds Objectives

Section 20.2 Unsaturated Hydrocarbons A. Alkenes and Alkynes Alkenes – hydrocarbon containing carbon-carbon double bonds  General formula C n H 2n Alkynes – hydrocarbons containing carbon-carbon triple bonds  General formula C n H 2n – 2

Section 20.2 Unsaturated Hydrocarbons A. Alkenes and Alkynes

Section 20.2 Unsaturated Hydrocarbons Exercise Name each of the following: a) 2,3,5-trimethyl-2-hexene b) 6-ethyl-3-methyl-3-octene

Section 20.2 Unsaturated Hydrocarbons Addition reactions – new atoms form single bonds to the carbons formerly involved in a double or triple bond  Hydrogenation – use H 2 as the reactant to be added Reactions of Alkenes  Halogenation – addition of halogen atoms Polymerization – joining of many small molecules to form a large molecule A. Alkenes and Alkynes

Section 20.2 Unsaturated Hydrocarbons B. Aromatic Hydrocarbons Aromatic hydrocarbons – cyclic unsaturated hydrocarbons with strong aromas

Section 20.2 Unsaturated Hydrocarbons B. Aromatic Hydrocarbons Benzene – simplest aromatic hydrocarbon

Section 20.2 Unsaturated Hydrocarbons C. Naming Aromatic Compounds Monosubstituted benzenes – use the substituent name as a prefix of benzene

Section 20.2 Unsaturated Hydrocarbons C. Naming Aromatic Compounds Disubstituted benzenes  Use numbers to indicate the position of substituents and the substituent name as a prefix of benzene.

Section 20.2 Unsaturated Hydrocarbons C. Naming Aromatic Compounds Complex aromatic molecules

Section 20.2 Unsaturated Hydrocarbons Benzene as a side group is called phenyl Phenyl (phenyl group): A portion of a molecular structure which is equivalent to benzene minus one hydrogen atom: -C 6 H 5 Chlorobenzene or Phenyl chloride

Section 20.3 Introduction to Functional Groups and Alcohols 1.To learn the common functional groups in organic molecules 2.To learn about simple alcohols and how to name them 3.To learn about how some alcohols are made and used 4.To learn about simple ethers and how to name them Objectives

Section 20.3 Introduction to Functional Groups and Alcohols A. Functional Groups Functional group – additional atom or groups of atoms (containing elements in addition to H and C) found on a mostly hydrocarbon molecule

Section 20.3 Introduction to Functional Groups and Alcohols B. Alcohols All alcohols contain the –OH group.

Section 20.3 Introduction to Functional Groups and Alcohols B. Alcohols

Section 20.3 Introduction to Functional Groups and Alcohols The different kinds of alcohols Alcohols fall into different classes depending on where the –OH is positioned on the chain of carbon atoms. There are some chemical differences between the various types. Primary, Secondary, and Tertiary alcohols will be discussed on the next several slides. Common alcohols: –Methanol-wood alcohol –Ethanol-as an antiseptic and in alcoholic beverages –Isopropanol-in rubbing alcohol

Section 20.3 Introduction to Functional Groups and Alcohols Primary Alcohols In a primary (1 o ) alcohol, the carbon which carries the – OH group is only attached to one alkyl group. Examples of primary alcohols: Ethanol 1-propanol 2-methyl-1-propanol

Section 20.3 Introduction to Functional Groups and Alcohols Secondary Alcohols In a secondary (2 o ) alcohol, the carbon with the –OH group attached is joined directly to two alkyl groups, which may be the same or different. Examples 2-propanol 2-butanol 3-pentanol

Section 20.3 Introduction to Functional Groups and Alcohols Tertiary Alcohols In a tertiary (3 o ) alcohol, the carbon with the –OH group attached is joined directly to three alkyl groups, which may be the same or different. Examples 2-methyl-2-propanol 2-methyl-2-butanol

Section 20.3 Introduction to Functional Groups and Alcohols C. Properties and Uses of Alcohols Methanol  starting material for making acetic acid and many adhesives, fibers and plastics  motor fuel Ethanol  Fermentation product  Fuel additive used to make gasohol

Section 20.3 Introduction to Functional Groups and Alcohols C. Properties and Uses of Alcohols Other alcohols  Ethylene glycol ( ethane-1,2-diol) – automotive antifreeze  Phenol (benzenol) – production of adhesives and plastics

Section 20.3 Introduction to Functional Groups and Alcohols C. Ethers An ether is a hydrocarbon with an oxygen sandwiched between the carbons. They tend to by very good solvents, much like water, and have relatively low reactivity.

Section 20.3 Introduction to Functional Groups and Alcohols Rules for Naming Ethers (common method) There are two predominate methods of naming ethers. The first is the common method and is most useful with simple ethers. (The second method is preferred; next slide) For the first method, if the carbon chains one side of the oxygen are considered alkyl groups you simply name the groups then write ether. CH 3 CH 2 O CH 3 Ethyl methyl ether

Section 20.3 Introduction to Functional Groups and Alcohols Rules for Naming Ethers (Preferred method) The other method follows the official IUPAC rules: Determine the longest alkyl chain for the root name. Treat the oxygen and the remaining carbons as aside chain. The prefix includes the alkyl chain with a suffix of oxy for the oxygen. CH 3 CH 2 O CH 3 methoxyethane

Section 20.3 Introduction to Functional Groups and Alcohols Practice Naming Ethers (answers next slide!)

Section 20.3 Introduction to Functional Groups and Alcohols Answers to Last Slide (a) Diisopropyl ether (a) Cyclopentyl propyl ether (a) 4-Bromo-1-methoxybenzene (d) 1-Methoxycyclohexene (d) Ethyl isobutyl ether

Section 20.3 Introduction to Functional Groups and Alcohols Preparation of Ethers Dehydration of two alcohols: Alkyl halide and alkoxide:

Section 20.4 Additional Organic Compounds 1.To learn about aldehydes and ketones 2.To learn to name aldehydes and ketones 3.To learn about some common carboxylic acids and esters 4.To learn about amines. 5.To learn how to name amines. 6.To learn about some common polymers Objectives

Section 20.4 Additional Organic Compounds A. Aldehydes and Ketones Carbonyl group – carbon oxygen group found in both aldehydes and ketones  Ketone – carbonyl group is bonded to two carbon atoms

Section 20.4 Additional Organic Compounds A. Aldehydes and Ketones  Aldehyde – carbonyl group always appears on the end of the hydrocarbon chain and has at least one H atom bonded to the carbonyl group

Section 20.4 Additional Organic Compounds A. Aldehydes and Ketones

Section 20.4 Additional Organic Compounds B. Naming Aldehydes and Ketones Aldehydes  Use the parent alkane name. Remove the  e and replace it with  al.

Section 20.4 Additional Organic Compounds B. Naming Aldehydes and Ketones Ketones  Use the parent alkane name. Remove the  e and replace it with  one. Use a number to indicate the position of the carbonyl group in the hydrocarbon chain.  Select the number so that the carbonyl has the lowest possible number. Propanone (acetone) 2-butanone (methyl-ethyl-ketone MEK)

Section 20.4 Additional Organic Compounds C. Carboxylic Acids and Esters Carboxylic acids – contains the carboxyl group  COOH General formula RCOOH Weak acids in solution

Section 20.4 Additional Organic Compounds C. Carboxylic Acids and Esters To name carboxylic acids  Use the parent alkane name. Remove the  e and replace it with  oic.

Section 20.4 Additional Organic Compounds C. Carboxylic Acids and Esters

Section 20.4 Additional Organic Compounds C. Carboxylic Acids and Esters Esters – a carboxylic acid reacts with an alcohol to form an ester and a water molecule  General formula

Section 20.4 Additional Organic Compounds C. Carboxylic Acids and Esters To name esters  Use the alkyl name from the alcohol followed by the acid name, where the –ic ending is replaced by –ate. isopropylethanoate

Section 20.4 Additional Organic Compounds Amines What are amines? The easiest way to think of amines is as near relatives of ammonia, NH 3. In amines, the hydrogen atoms in the ammonia have been replaced one at a time by hydrocarbon groups. On this page, we are only looking at cases where the hydrocarbon groups are simple alkyl groups.

Section 20.4 Additional Organic Compounds The different kinds of amines Amines fall into different classes depending on how many of the hydrogen atoms are replaced. PrimarySecondaryTertiary In a primary (1°) amine, one carbon group is bonded to the nitrogen atom. A secondary (2°) amine has two carbon groups. A tertiary (3°) amine has three carbon groups.

Section 20.4 Additional Organic Compounds Common Names of Amines Simple amines are named as alkylamines. The alkyl groups bonded to the N atom are listed in alphabetical order in front of amine.

Section 20.4 Additional Organic Compounds IUPAC Names of Amines In the IUPAC system, amines are named as alkanamines. The –e in the alkane name of the longest chain is changed to –amine. The chain is numbered to locate the amine group and substituents.

Section 20.4 Additional Organic Compounds Primary amines In primary amines, only one of the hydrogen atoms in the ammonia molecule has been replaced. That means that the formula of the primary amine will be R-NH 2 where "R" is an alkyl group. Examples include: Methanamine EthanaminePropanamineIsopropanamine

Section 20.4 Additional Organic Compounds The common name at this level is methylamine and, similarly, the second compound drawn above is usually called ethylamine. Where there might be confusion about where the -NH 2 group is attached to a chain, the simplest way of naming the compound is to use the "amino" form.

Section 20.4 Additional Organic Compounds Secondary amines In a secondary amine, two of the hydrogens in an ammonia molecule have been replaced by hydrocarbon groups. At this level, you are only likely to come across simple ones where both of the hydrocarbon groups are alkyl groups and both are the same. Dimethanaminediethanamine

Section 20.4 Additional Organic Compounds Tertiary amines In a tertiary amine, all of the hydrogens in an ammonia molecule have been replaced by hydrocarbon groups. Again, you are only likely to come across simple ones where all three of the hydrocarbon groups are alkyl groups and all three are the same. The naming is similar to secondary amines. For example:

Section 20.4 Additional Organic Compounds Physical Properties of Amines We will look at the boiling point difference on the next several slides.

Section 20.4 Additional Organic Compounds Primary amines It is useful to compare the boiling point of methylamine, CH 3 NH 2, with that of ethane, CH 3 CH 3. Both molecules contain the same number of electrons and have, as near as makes no difference, the same shape. However, the boiling point of methylamine is - 6.3°C, whereas ethane's boiling point is much lower at °C. The reason for the higher boiling points of the primary amines is that they can form hydrogen bonds with each other as well as van der Waals dispersion forces and dipole-dipole interactions.

Section 20.4 Additional Organic Compounds Secondary amines For a fair comparison you would have to compare the boiling point of dimethylamine with that of ethylamine. They are isomers of each other - each contains exactly the same number of the same atoms. The boiling point of the secondary amine is a little lower than the corresponding primary amine with the same number of carbon atoms. Secondary amines still form hydrogen bonds, but having the nitrogen atom in the middle of the chain rather than at the end makes the permanent dipole on the molecule slightly less. The lower boiling point is due to the lower dipole-dipole attractions in the dimethylamine compared with ethylamine.

Section 20.4 Additional Organic Compounds Tertiary amines This time to make a fair comparison you would have to compare trimethylamine with its isomer 1-aminopropane. If you look back at the table on slide 18, you will see that the trimethylamine has a much lower boiling point (3.5°C) than 1-aminopropane (48.6°C). In a tertiary amine there aren't any hydrogen atoms attached directly to the nitrogen. That means that hydrogen bonding between tertiary amine molecules is impossible. That's why the boiling point is much lower.

Section 20.4 Additional Organic Compounds Solubility in water The small amines of all types are very soluble in water. In fact, the ones that would normally be found as gases at room temperature are normally sold as solutions in water - in much the same way that ammonia is usually supplied as ammonia solution. Smell The very small amines like methylamine and ethylamine smell very similar to ammonia - although if you compared them side by side, the amine smells are slightly more complex. As the amines get bigger, they tend to smell more "fishy", or they smell of decay.

Section 20.4 Additional Organic Compounds D. Polymers Polymers – large chainlike molecules made from many small molecules called monomers  Simplest polymer – polyethylene  Polyethylene results from addition polymerization.

Section 20.4 Additional Organic Compounds D. Polymers Condensation polymerization – a small molecule (often water) is released for each addition of a monomer to the polymer chain Copolymer – 2 different types of monomers combine to form the chain  Nylon (co-polymer)polymer

Section 20.4 Additional Organic Compounds Sodium Silicate polymer When sodium silicate and ethyl alcohol are put together, the silicate particles begin to link up with each other to form long chains as the ethyl groups (sometimes shown as "R") replace oxygen atoms in the silicate ion. (Some become cross-linked between chains.) Water molecules are by-products of the formation of the polymerization bond. The large molecule is a solid. It is a type of silicone polymer.