GS105: Chapter 12 Energy & Hydrocarbons Hydrocarbons Aromatics Fuel

Properties of Organic Compounds An organic compound Is a compound made from carbon atoms. Has one or more C atoms. Has many H atoms. May also contain O, S, N, and halogens. Typical organic compounds Have covalent bonds. Have low melting points. Have low boiling points. Are flammable. Are soluble in nonpolar solvents. Are not soluble in water. Oil (organic) and water (inorganic)

Organic vs. Inorganic Propane, C3H8, is an organic compound used as a fuel. NaCl, salt, is an inorganic compound composed of Na+ and Cl− ions. Why is propane an organic compound, but NaCl is not? Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Organic vs. Inorganic Ionic Polar most H2O sol Covalent Nonpolar C3H8 (propane) Inorganic NaCl (salt) Bonding Polarity, Solubility Melting point Boiling point Flammability Covalent Ionic Nonpolar Polar most H2O sol not H2O sol Low -188oC High 800oC Low -42oC High 1413oC High Low

Learning Check Identify each characteristic as most typical of compounds that are (I) inorganic or (O) organic. 1. Has a high melting point 2. Is not soluble in water 3. Has a formula CH3─CH2─CH3 4. Has a formula MgCl2 5. Burns easily in air 6. Has covalent bonds

Solution Identify each characteristic as most typical of compounds that are (I) inorganic or (O) organic. I 1. Has a high melting point O 2. Is not soluble in water O 3. Has a formula CH3─CH2─CH3 I 4. Has a formula MgCl2 O 5. Burns easily in air O 6. Has covalent bonds

Combustion of Hydrocarbons Undergo combustion by reacting with oxygen to produce carbon dioxide, water, and energy. Are typically not very reactive due to strong C-C single bonds. Hydrocarbon + O2  CO2 + H2O + energy

Learning Check Propane is used to provide heat for cooking or warming a room. Write a balanced equation for the complete combustion of propane.

Solution C3H8 + 5O2  3CO2 + 4H2O (Balanced) Unbalanced equation Balance C C3H8 + O2  3CO2 + H2O Balance H C3H8 + O2  3CO2 + 4H2O Balance O To balance the atoms in the formula C3H8, we place a coefficient of 3 in front of CO2 and a coefficient of 4 in front of H2O. The total O in the products is 10 O (6 O in 3CO2 and 4 O in 4 H2O). To balance the 10 O, a coefficient of 5 is placed in front of the O2. C3H8 + 5O2  3CO2 + 4H2O (Balanced)

Learning Check Write a balanced equation for the reaction for the complete combustion of heptane C7H16.

Solution C7H16 + 11O2  7CO2 + 8H2O C7H16 + O2  CO2 + H2O Balanced equation: C7H16 + 11O2  7CO2 + 8H2O

Learning Check Write the combustion reaction for ethane and balance.

Solution 2C2H6 + 7O2  4CO2 + 6H2O balanced Write the combustion reaction for ethane and balance. ethane CH3CH3 = C2H6 C2H6 + O2  2CO2 + 3H2O C2H6 + 7 O2  2CO2 + 3H2O C2H6 + 7/2 O2  2CO2 + 3H2O Multiply through by 2 to clear fraction 2C2H6 + 7O2  4CO2 + 6H2O balanced

Less than 0 Boiling points (oC) 35-100 35-215 35-300 300-400 350-400

Fractional Distillation of Crude Oil The hydrocarbons in crude oil are Separated by boiling points. Heated to higher temperatures to produce gases that can be removed and cooled.

Octane Rating Catalytic cracking/Reforming

BP Crude Oil Refinery (Distillation Tower) Carson, California

Writing Formulas for Carbon Compounds In carbon compounds Carbon has 4 valence electrons and hydrogen has 1. • • C • H • To achieve an octet, C forms four bonds. H H   H  C  H H C H H H CH4 , methane

Structural Formulas Alkanes are written with structural formulas that are Expanded to show each bond. Condensed to show each carbon atom and its attached hydrogen atoms. Expanded Condensed H H C H CH4 , methane In methane, CH4 the four valence electrons of carbon are shared with the single electrons of four hydrogen (H) atoms. Each pair of electrons is a single bond, which can be drawn as a line. When a structure is drawn to show each bond, it is called a complete structural formula.

Organic Compounds with More Carbon Atoms In organic molecules with more carbon atoms, Valence electrons are shared. Covalent bonds form between carbon and carbon atoms. Covalent bonds form between carbon and hydrogen atoms. H H H H • • • • H  C  C  H H C C H H H H H ethane, CH3─CH3

Tetrahedral Structure of Carbon In molecules with two or more carbon atoms, each carbon atom with four single bonds has a tetrahedral shape.

Expanded and Condensed Structures Structural formulas

Names of Alkanes The names of alkanes Are determined by the IUPAC (International Union of Pure and Applied Chemistry) system. Use a prefix to indicate the number of carbons in a chain. End in –ane.

Learning Check A. Give the name of each compound: 1) CH3—CH3 2) CH3—CH2—CH3 3) CH3—CH2—CH2—CH2—CH2—CH3 B. Write the condensed structural formula of pentane.

Solution A. Give the name of each compound: 1) CH3—CH3 ethane 2) CH3—CH2—CH3 propane 3) CH3—CH2—CH2—CH2—CH2—CH3 hexane B. Write the condensed structural formula of pentane. CH3—CH2—CH2—CH2—CH3

Line-Bond Formulas Because each C atom has a tetrahedral arrangement, the order of atoms is not a straight line, but a zigzag pattern. A line-bond formula abbreviates the carbon atoms and shows only the zigzag pattern of bonds from carbon atom to carbon atom.

Conformations The groups attached to a C-C single bond Rotate around the bond, Give different relative arrangements called conformations. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Conformations of Butane Rotation of the end CH3- provides different conformations for butane. Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cumming

Some Structures for Butane

Hexane has Six Carbon Atoms Is an alkane with 6 carbon atoms in a continuous chain. Has a “zig-zag” look because each carbon atom is at the center of a tetrahedron. Is represented by a ball-and-stick model as Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Learning Check A. Write the condensed formula for: H H H H H H C C C C C H H H H H H B. What is its molecular formula? C. What is its name?

Solution A. CH3CH2CH2CH2CH3 B. C5H12 C. pentane

Learning Check Write the condensed structural formula for A. ethane B. heptane

Solution Write the condensed structural formula for A. ethane CH3─CH3 B. heptane CH3─CH2─CH2─CH2─CH2─CH2─CH3

Cycloalkanes Cycloalkanes Are cyclic alkanes. Have 2H fewer than the open chain. Are named by using the prefix cyclo- before the name of the alkane chain with the same number of carbon atoms. Cyclopropane Cyclobutane Cyclopentane Cyclohexane

Learning Check Name the following: A. CH3─CH2─CH2─CH3 B. C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3 D.

Solution Name the following: A. CH3─CH2─CH2─CH3 butane B. cyclopropane C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3 octane D. cyclohexane

Isomers of Butane Isomers Have the same molecular formula. Have different atom arrangements. Of butane (C4H10) consist of a straight chain and a branched chain each with 4 carbon atoms. branch Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings

Naming Substituents In the IUPAC system, A carbon branch is named as an alkyl group. Halogen atoms are named as halo.

Naming Substituents In the IUPAC system, Names of side groups methyl ethyl propyl Isopropyl n-butyl sec-butyl Isobutyl tert-butyl or t-butyl In the IUPAC system, A carbon branch is named as an alkyl group. Halogen atoms are named as halo.

Naming Substituents In the IUPAC system, Names of side groups Fluoro Chloro Bromo Iodo Hydroxy In the IUPAC system, A carbon branch is named as an alkyl group. Halogen atoms are named as halo.

Alkanes with Alkyl Groups CH3 CH3 CH CH3 methylpropane methyl groups CH3 CH3 CH3 CH CH2 CH CH3 2,4-dimethylpentane

Guide to Naming Alkanes Give the name of CH3 CH3   CH3─CH─CH─CH3 STEP 1 Longest chain is butane. STEP 2 Number chain. CH3 CH3   1 2 3 4 STEP 3 Locate substituents and name. 2,3-dimethylbutane

Learning Check Write the IUPAC name for Cl CH3   CH3─CH2─CH─CH─CH3

Solution STEP 1 Longest chain is pentane. STEP 2 Number chain from end nearest substituent. Cl CH3 (nearest end)   CH3─CH2─CH─CH─CH3 5 4 3 2 1 STEP 3 Locate substituents and name alphabetically. 3-chloro-2-methylpentane

Learning Check Give the IUPAC name for the following: CH3 CH3 | | | | CH3─CH─CH2 ─CH─CH2─CH3

Solution A. CH3 CH3 | | CH3─CH─CH2 ─CH─CH2─CH3 2,4-dimethylhexane | | CH3─CH─CH2 ─CH─CH2─CH3 2,4-dimethylhexane 1 2 3 4 5 6 2, 4-dimethylhexane 2, 4 dimethyl hexane Location of Two CH3- groups 6 carbon main chain branches on attached with single C-C bonds main chain

Learning Check Draw the condensed structural formula for 2-bromo-4-chlorobutane.

Solution STEP 1 Longest chain has 4 carbon atoms. C─C─C─C STEP 2 Number chain and add substituents. Br  C ─ C ─ C ─ C ─ Cl 1 2 3 4 STEP 3 Add hydrogen to complete 4 bonds to each C. CH3─CH─CH2─CH2─Cl

Learning Check Write three isomers of C5H12 and name each.

Solution A chain of 5 carbon atoms CH3─CH2─CH2─CH2─CH3 pentane A chain of 4 carbon atoms and 1 carbon branch CH3 │ CH3─CH─CH2─CH3 2-methylbutane A chain of 3 carbon atoms and 2 carbon branches CH3─C─CH3 2,2-dimethylpropane

Alkanes with 1-4 Carbon Atoms Gases Alkanes with 1-4 carbon atoms are Methane, ethane, propane, and butane. Gases at room temperature. Used as heating fuels.

Alkanes with 5-17 Carbon Atoms Liquids Alkanes with 5-8 carbon atoms are Liquids at room temperature. Pentane, hexane, heptane, and octane. Very volatile. Used to make gasoline. Alkanes with 9-17 carbon atoms Are liquids at room temperature Have higher boiling points. Are found in kerosene, diesel, and jet fuels.

Alkanes with 18 or more Carbon Atoms Solids Alkanes with 18 or more carbon atoms Have high molar masses. Are waxy solids at room temperature. Used in waxy coatings of fruits and vegetables.

Boiling Points of Pentanes BPs of alkanes Are lowest of organic compounds. Increase with larger molecules due to increased dispersion forces. Decrease for branched alkanes. Increase for cycloalkanes.

Learning Check For the following pairs of hydrocarbon, which one has the higher boiling point? Why? 1. butane or octane 2. hexane or 2,3-dimethylbutane

Solution For the following pairs of hydrocarbon, which one has the higher boiling point? Why? 1. butane or octane octane has more carbon atoms 2. hexane or 2,3-dimethylbutane hexane is not branched

Heteroatoms in Organic Compounds In organic molecules, C atoms form bonds Mostly with H and other C atoms. Sometimes Heteroatoms: atoms of O, N, S, and halogens F, Cl, and Br.

Functional Groups Functional groups are A characteristic feature of organic molecules that behave in a predictable way. Composed of an atom or group of atoms. Groups that replace a H in the corresponding alkane. A way to classify families of organic compounds.

Some Functional Groups

Unsaturated Hydrocarbons Alkenes Alkynes Unsaturated hydrocarbons Have fewer hydrogen atoms attached to the carbon chain than alkanes. Are alkenes with double bonds. Are alkynes with triple bonds. ethylene acetylene Is used as fuel for welders torches. Is used to accelerate the ripening of fruits.

Naming Alkenes & Alkynes Use the corresponding alkane name. Change the ending to ­ene or -yne Alkene IUPAC Common H2C=CH2 ethene ethylene H2C=CH─CH3 propene propylene cyclohexene Alkyne IUPAC Common HC≡CH ethyne acetylene HC≡C─CH3 propyne

Comparing Names of Alkanes, Alkenes, and Alkynes

Naming Alkenes Write the IUPAC name for CH2=CH─CH2─CH3 and STEP 1 Name the longest carbon chain butene STEP 2 Number the chain from the double bond CH2=CH─CH2─CH3 1-butene 1 2 3 4 CH3─CH=CH─CH3 2-butene

Naming Alkenes with Substituents CH3 │ Write the IUPAC name for CH3─CH─CH=CH─CH3 STEP 1 Name the longest carbon chain pentene STEP 2 Number the chain from the double bond CH3─CH─CH=CH─CH3 2-pentene 5 4 3 2 1 STEP 3 Give the location of each substituent 4-methyl- 2-pentene

Naming Alkynes with Substituents CH3 │ Write the IUPAC name for HC≡C─CH─CH3 1 2 3 4 STEP 1 Name the longest carbon chain butyne STEP 2 Number the chain from the double bond 1-butyne STEP 3 Give the location of each substituent 3-methyl-1-butyne

Learning Check Write the IUPAC name for each of the following: 1. CH2=CH─CH2─CH3 2. CH3─CH=CH─CH3 CH3 | 3. CH3─CH=C─CH3 4. CH3─CC─CH3

Solution Write the IUPAC name for each of the following: 1. CH2=CH─CH2─CH3 1-butene 2. CH3─CH=CH─CH3 2-butene CH3 | 3. CH3─CH=C─CH3 2-methyl-2-butene 4. CH3─CC─CH3 2-butyne

Cis and Trans Isomers In an alkene, cis and trans isomers are possible because the double bond Is rigid. Cannot rotate. Has groups attached to the carbons of the double bond that are fixed relative to each other. CH3 CH3 CH3 CH = CH CH = CH cis trans CH3

Cis-Trans Isomers Cis-trans isomers Can be modeled by making a “double bond” with your fingers with both thumbs on the same side or opposite from each other.

Cis-Trans Isomers Cis-trans isomers occur when different groups are attached to the double bond. In a cis isomer, groups on the same side of C=C In the trans isomer, the groups on opposite sides.

Pheromones A pheromone Is a chemical messenger emitted by insects in tiny quantities. Called bombykol emitted by the silkworm moth to attract other moths has one trans and one cis double bond.

Learning Check Identify each has having cis or trans groups

Solution trans-2-butene Neither cis nor trans 1,1-dichloropropene cis-1,2-dibromoethene trans-2-butene Neither cis nor trans 1,1-dichloropropene Identical atoms on one C; no cis or trans

Hydrogenation In hydrogenation, Hydrogen atoms add to the carbon atoms of a double bond or triple bond. A catalyst such as Pt or Ni is used to speed up the reaction.

Hydrogenation of Oils Adding H2 to double bonds in vegetable oils produces Compounds with higher melting points. Solids at room temperature such as margarine, soft margarine, and shortening.

Learning Check Write an equation for the hydrogenation of 1-butene using a platinum catalyst.

Solution Write an equation for the hydrogenation of 1-butene using a platinum catalyst. Pt CH2=CH─CH2─CH3 + H2 CH3─CH2─CH2─CH3

Trans Fats In vegetable oils, the unsaturated fats usually contain cis double bonds. During hydrogenation, some cis double bonds are converted to trans double bonds (more stable) causing a change in the fatty acid structure If a label states “partially” or “fully hydrogenated”, the fats contain trans fatty acids.

Learning Check (T) True or (F) False A. ____ There are more unsaturated fats in vegetable oils. B. ____ Hydrogenation converts some cis-double bonds to trans- double bonds. C. ____ Animal fats have more unsaturated fats.

Solution (1) True or (2) False A. T There are more unsaturated fats in vegetable oils. B. T Hydrogenation of oils converts some cis-double bonds to trans- double bonds. C. F Animal fats have more unsaturated fats.

Aromatic Compounds Benzene Has 6 electrons shared equally among the 6 C atoms. Is also represented as a hexagon with a circle drawn inside. Cancer causing because so flat Benzopyrene Naphthalene In smoke

Common Aromatic Compounds toluene aniline phenol (methylbenzene) (benzenamine) (hydroxybenzene) Trinitrotoluene TNT

Aromatic Compounds in Nature and Health Vanillin Aspirin Ibuprofen Acetaminophen Not Cancer causing because not flat