Chapter 5 Chemical Quantities and Reactions

1. Chapter 5 Chemical Quantities and Reactions 5.8 Energy in Chemical Reactions

2. Molecules Must Collide for Reaction Three conditions for a reaction to occur are: 1. collision: The reactants must collide. 2. orientation: The reactants must align properly to break and form bonds. 3. energy: The collision must provide the energy of activation.

3. Exothermic Reaction In an exothermic reaction, • heat is released • the energy of the products is less than the energy of the reactants • heat is a product C(s) + 2H2(g) CH4(g) + 18 kcal

4. Endothermic Reactions In an endothermic reaction, • heat is absorbed • the energy of the products is greater than the energy of the reactants • heat is a reactant (added) N2(g) + O2(g) + 43.3 kcal  2NO(g)

5. Learning Check Identify each reaction as exothermic or endothermic. A. N2(g) + 3H2(g) 2NH3(g) + 22 kcal B. CaCO3(s) + 133 kcal CaO(s) + CO2(g) C. 2SO2(g) + O2(g) 2SO3(g) + heat

6. Solution Identify each reaction as exothermic or endothermic. A. N2(g)+ 3H2(g)2NH3(g)+ 22 kcal Exothermic B. CaCO3(s) + 133 kcal CaO(s) + CO2(g) Endothermic C. 2SO2(g) + O2(g) 2SO3(g) + heat Exothermic

7. Reaction Rate The reaction rate • is the speed at which reactant is used up • is the speed at which product forms • increases when temperature rises because reacting molecules move faster, providing more colliding molecules with energy of activation • increases with increase in concentration of reactants

8. Catalyst A catalyst • increases the rate of a reaction • lowers the energy of activation • is not used up during the reaction

9. Factors That Increase Reaction Rate

10. Learning Check State the effect of each on the rate of reaction as increases, decreases, or has no effect: A. increasing the temperature B. removing some of the reactants C. adding a catalyst D. placing the reaction flask in ice E. increasing the concentration of one of the reactants

11. Solution State the effect of each on the rate of reaction as increases, decreases, or has no effect: A. increasing the temperature increases B. removing some of the reactants decreases C. adding a catalyst increases D. placing the reaction flask in ice decreases E. increasing the concentration of one of the reactant increases

12. Chapter 10 Introduction to Organic Chemistry: Alkanes 10.5 Functional Groups

13. Elements in Organic Compounds In organic molecules, carbon atoms bond • with four bonds • mostly with H and other C atoms • sometimes to O, N, S • sometimes to halogens F, Cl, and Br

14. Elements in Organic Compounds

15. 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 hydrogen atom in the corresponding alkane • a way to classify families of organic compounds

16. Alkenes, Alkynes, and Aromatic Compounds Alkenes contain a double bond between adjacent carbon atoms. Alkynes contain a triple bond. Aromatic compounds contain a ring of six carbon atoms called benzene.

17. Comparing Alkenes, Alkynes, and Aromatic Compounds

18. Learning Check Identify the following compounds as an alkene, alkyne, or aromatic compound. A. B. C.

19. Solution Identify the following compounds as an alkene, alkyne or aromatic compound. A. aromatic B. alkene C. alkyne

20. Alcohols, Thiols, and Ethers An alcoholcontains the hydroxyl (−OH)functional group. Athiol contains the thiol (−SH) functional group. Anether contains an oxygen atom bonded to two carbon atoms (COC) functional group.

21. Aldehydes and Ketones An aldehydecontains a carbonylgroup (C=O), which is a carbon atom with a double bond to an oxygen atom. The carbonyl carbon is attached to a hydrogen. In a ketone,the carbon of the carbonyl group (C=O) is attached to two carbon atoms.

22. Carboxylic Acids and Esters Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group. COOH An ester contains the carboxyl group between carbon atoms. COOCH3

23. Amines Amines • have a functional group that contains a nitrogen atom • are derivatives of ammonia, NH3, in which one, two, or three hydrogen atoms are replaced with carbons

24. Amides Amides • have an amine group instead of an OH group on the carbonyl carbon • are an important biological functional group, the simplest amide being urea

25. Classification of Organic Compounds

26. Learning Check Classify each of the following as an alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide. A. B. C. D. E.

27. Solution Classify each of the following as an alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide. A. B. C. D. E. alcohol ether amine carboxylic acid ester

28. Concept Map – Organic Compounds

29. Chapter 11 Unsaturated Hydrocarbons 11.1 Alkenes and Alkynes

30. Saturated Hydrocarbons Saturated hydrocarbons • have the maximum number of hydrogen atoms attached to each carbon atom • are alkanes and cycloalkanes with single C–C bonds CH3–CH2–CH3

31. Unsaturated Hydrocarbons Unsaturated hydrocarbons • have fewer hydrogen atoms attached to the carbon chain than alkanes • are alkenes with double bonds • are alkynes with triple bonds Ball-and-stick models of ethene and ethyne show functional groups of double or triple bonds and bond angles.

32. Ethene (Ethylene) Ethene, or ethylene, • is the simplest alkene, with the formula C2H4 • has two carbon atoms connected by a double bond • has two H atoms bonded to each C atom • is flat, with all the C and H atoms in the same plane • is a plant hormone used to accelerate the ripening of fruits

33. Fragrant Alkenes The odors associated with the smell of lemons, oranges, roses, and lavender are due to volatile compounds that are synthesized by the plants.

34. Ethyne (Acetylene) The simplest alkyne is ethyne, which has the common name of acetylene. Acetylene is a fuel used in welding.

35. Naming Alkenes and Alkynes When the carbon chain of an alkene or alkyne has four or more C atoms, number the chain to give the lowest number to the first carbon in the double or triple bond. CH2=CHCH2CH3 1-butene 1 2 3 4 CH3CH=CHCH3 2-butene 1 2 3 4 CH3CH2C=CCH3 2-pentyne 5 4 3 2 1

36. Guide to Naming Alkenes and Alkynes

37. Naming Alkenes Using the IUPAC system, name the following compounds: CH3 CH3 CH3 A. CH3CHH2C=CH2 B. H2C=CHCHCHCH3 Step 1Name the longest carbon chain that contains the double bond. Use the ending ene for alkenes. CH3 CH3 CH3 A. CH3CHH2C=CH2 B. H2C=CHCHCHCH3 butene pentene

38. Naming Alkenes Step 2Number the longest carbon chain starting from the end nearer the double bond. CH3 CH3 CH3 A. CH3CHH2C=CH2 B. H2C=CHCHCHCH3 1-butene1-pentene Step 3Give the location and name of each substituent (in alphabetical order) as a prefix to the alkene name. CH3CH3 CH3 A. CH3CHH2C=CH2 B. H2C=CHCHCHCH3 3-methyl-1-butene3,4-dimethyl-1-pentene

39. Naming Alkynes Using the IUPAC system, name the following compound: CH3CH3 HC CCHCHCH3 Step 1Name the longest carbon chain that contains the triple bond. Use the ending yne for alkynes. CH3 CH3 HC CCHCHCH3 pentyne

40. Naming Alkynes Step 2Number the longest carbon chain starting from the end nearer the triple bond. CH3 CH3 HC CCHCHCH3 1-pentyne Step 3Give the location and name of each substituent (in alphabetical order) as a prefix to the alkyne name. CH3 CH3 HC CCHCHCH3 3,4-dimethyl-1-pentyne

41. Chapter 11 Unsaturated Hydrocarbons 11.2 Cis–Trans Isomers

42. Cis and Trans Isomers In an alkene, the double bond • is rigid • holds attached groups in fixed positions • makes cis–trans isomers possible

43. Cis–Trans Isomers In cis–trans isomers, • there is no rotation around the double bond in alkenes • groups attached to the double bond are fixed relative to each other You can make a “double bond” with your fingers with both thumbs on the same side or opposite from each other.

44. Cis–Trans Isomers Two isomers are possible when the groups attached to each side of the double bond are different. • In a cis isomer, the alkyl groups are attached on one side of the double bond and H atoms are on the other side. • In the trans isomer, the groups and H atoms are attached on opposite sides. Ball-and-stick models of the cis and trans isomers of 2-butene.

45. Cis–Trans Isomerism • Alkenes cannot have cis–trans isomers if a carbon atom in the double bond is attached to identical groups. Identical Identical 2-Bromopropene1,1-Dibromoethene (not cis or trans) (not cis or trans) H H Br H

46. Cis–Trans Isomers in Nature • Insects emit tiny quantities of pheromones, which are chemicals that send messages. • The silkworm moth attracts other moths by emitting bombykol, which has one cis and one trans double bond. Pheromones allow insects to attract mates from a great distance.

47. Naming Cis–Trans Isomers The prefix of cis or trans is placed in front of the alkene name when the compound is a cisortrans isomer. cis trans cis-1,2-dibromoethenetrans-1,2-dibromoethene

48. Learning Check Name each, using cis or transprefixes when needed.

49. Solution Name each, using cis or trans prefixes when needed. cis-1,2-dibromoethene trans-2-butene 1,1-dichloropropene

50. Chapter 11 Unsaturated Hydrocarbons 11.4 Polymers of Alkenes