Introductory Chemistry, 3rd Edition Nivaldo Tro

1. Roy Kennedy Massachusetts Bay Community College Wellesley Hills, MA Introductory Chemistry, 3rd EditionNivaldo Tro

2. Tro's Introductory Chemistry, Chapter 18 2 What Is Organic Chemistry? Organic chemistry is a branch of chemistry that focuses on compounds that contain carbon. Except CO, CO2, carbonates, and carbides. Even though organic compounds only contain a few elements, the unique ways carbon atoms can attach together to form molecules leads to millions of different organic compounds.

3. Tro's Introductory Chemistry, Chapter 18 3 The Chemistry of Life Life as we know it is because of organic chemistry. Organic molecules can be very large and complex. It is this complexity of large organic molecules that allows the complex functions of the cells to occur.

4. Tro's Introductory Chemistry, Chapter 18 4 Classifying Pure Substances,the Modern Way

5. Tro's Introductory Chemistry, Chapter 18 5 What’s Special About Organic Compounds? Organic compounds tend to be molecular. Mainly composed of just six nonmetallic elements. C, H, O, N, S, and P. Compounds found in all three states. Solids, liquids, and gases. Solids tend to have low melting points. Solubility in water varies depending on which of the other elements are attached to C and how many there are. CH3OH is miscible with water; C10H21OH is insoluble.

6. Tro's Introductory Chemistry, Chapter 18 6 What’s So Special About Carbon? Carbon atoms can do some unique things that other atoms cannot. Carbon can bond to as many as four other atoms. Bonds to carbon are very strong and nonreactive. Carbon atoms can attach together in long chains. Carbon atoms can attach together to form rings. Carbon atoms can form single, double, or triple bonds.

7. Tro's Introductory Chemistry, Chapter 18 Carbon Carbon forms four bonds. When C has four single bonds, the shape is tetrahedral. When C has one triple + one single or two double bonds, the shape is linear. When C has two single + one double bond, the shape is trigonal planar.

8. Practice—Predict the Shape Around Each C Atom. HCN CH3CH2CH3 H2CNH HCO2H C2H3Cl C3H4

9. HCN CH3CH2CH3 H2CNH HCO2H C2H3Cl C3H4 Practice—Predict the Shape Around Each C Atom, Continued.

10. Tro's Introductory Chemistry, Chapter 18 10 Hydrocarbons Hydrocarbons contain only C and H. Two classes of hydrocarbons: saturated or unsaturated. Insoluble in water. No polar bonds to attract water molecules. May be chains or rings. Ring molecules have less H than chain so that the ends can join. Chains may be straight or branched. Rings may be aliphatic or aromatic.

11. Uses of Hydrocarbons

12. Tro's Introductory Chemistry, Chapter 18 12 Saturated Hydrocarbons A saturated hydrocarbon has all C—C single bonds. It is saturated with hydrogens. Saturated hydrocarbons are called alkanes. Chain alkanes have the general formula CnH2n+2. Chains may be straight or branched. “Normal” isomer is the straight chain. Ring alkanes have two fewer Hs per ring than the corresponding chain isomer.

13. Tro's Introductory Chemistry, Chapter 18 13 Unsaturated Hydrocarbons Unsaturated hydrocarbons have one or more C=C double bonds, C?C triple bonds, or aromatic rings. Unsaturated hydrocarbons that contain C=C are called alkenes. The general formula of a monounsaturated chain alkene is CnH2n. Remove two more Hs for each additional unsaturation. Unsaturated hydrocarbons that contain C?C are called alkynes. The general formula of a monounsaturated chain alkyne is CnH2n-2. Remove four more Hs for each additional unsaturation.

14. Some Unsaturated Hydrocarbons

15. Aromatic Hydrocarbons Aromatic hydrocarbons contain a ring structure that seems to have C=C, but doesn’t behave that way. The most prevalent example is benzene. C6H6. Other compounds have the benzene ring with other groups substituted for some of the Hs. Tro's Introductory Chemistry, Chapter 18 15

16. Tro's Introductory Chemistry, Chapter 18 16 Hydrocarbons

17. Types of Hydrocarbons

18. Tro's Introductory Chemistry, Chapter 18 18 Practice—Assuming Only Chains with a Maximum of One Unsaturation, Decide if Each of the Following Molecular Formulas Represents an Alkane, Alkene, or Alkyne. C14H28 C25H52 C12H10

19. Tro's Introductory Chemistry, Chapter 18 19 Practice—Assuming Only Chains with a Maximum of One Unsaturation, Decide if Each of the Following Molecular Formulas Represents an Alkane, Alkene, or Alkyne, Continued. C14H28 Alkene. C25H52 Alkane. C12H10 Alkyne.

20. 20 Formulas Molecular formulas just tell you what kinds of atoms are in the molecule, but they don’t tell you how they are attached. Structural formulas show you the attachment pattern in the molecule. Models not only show you the attachment pattern, but give you an idea about the shape of the molecule.

21. Condensed Structural Formulas Attached atoms listed in order. Central atom with attached atoms. Follow normal bonding patterns. Use to determine position of multiple bonds. () used to indicate more than one identical group attached to same previous central atom. Unless () group listed first in which case attached to next central atom.

22. Carbon Skeleton Formulas A.k.a. line-angle formulas. Used very often with ring structures. Each angle, and its beginning and end represent a C atom. H omitted on C. Included on functional groups. Multiple bonds indicated. Double line is double bond; triple line is triple bond.

24. Tro's Introductory Chemistry, Chapter 18 24 Example 18.2—Write the Structural and Condensed Formula for the n-Alkane C8H18. Connect the C atoms in a row. Carbon skeleton. Add H to complete four bonds on each C. Middle C gets 2 Hs. End C gets 3 Hs. The condensed formula has the H attached to each C written directly after it.

25. Practice—Write a Complete Structural Formula for C7H16.

26. Practice—Write a Complete Structural Formula for C7H16, Continued.

27. Tro's Introductory Chemistry, Chapter 18 27 Alkanes—Physical Properties Nonpolar molecules, intermolecular attractions due to induced dipoles. Both boiling points and melting points generally increase as the size of the molecule increases. Insoluble in water, commonly used as nonpolar solvents. Less dense than water, density increases with size.

28. Tro's Introductory Chemistry, Chapter 18 28 Physical Properties of n–Alkanes

29. Select the Molecule in Each Pair with the Higher Boiling Point.

30. Select the Molecule in Each Pair with the Higher Boiling Point, Continued.

31. Tro's Introductory Chemistry, Chapter 18 31 Naming Each name consists of three parts: Prefix. Indicates position, number, and type of branches. Indicates position, number, and type of each functional group. Parent. Indicates the length of the longest carbon chain or ring. Suffix. Indicates the type of hydrocarbon. -ane, -ene, -yne Certain functional groups.

32. Tro's Introductory Chemistry, Chapter 18 32 Naming Alkanes Find the longest, continuous carbon chain. Number the chain from the end closest to a branch. If first branches equal distance, use the next in. Name branches as alkyl groups. Locate each branch by preceding its name with the carbon number on the chain. List branches alphabetically. Do not count n-, sec-, t-, but count iso. Use prefix if more than one of the same group is present. di-, tri-, tetra-, penta-, hexa-. Do not count in alphabetizing.

33. Tro's Introductory Chemistry, Chapter 18 33 Examples of Naming Alkanes

34. Tro's Introductory Chemistry, Chapter 18 34 Naming Alkenes and Alkynes Find longest chain containing multiple bond. Alkene takes precedence over alkyne. Change suffix on main name from -ane to -ene for base name of alkene, or to –yne for the base name of the alkyne. Number chain from end closest to multiple bond. Number in front of main name indicates first carbon of multiple bond.

35. Tro's Introductory Chemistry, Chapter 18 35 Aromatics Benzene Resonance hybrid. Does not react like alkenes. Reactions are generally substitutions for H.

36. Tro's Introductory Chemistry, Chapter 18 36 Line-Angle Formulas Each angle, and beginning and end, represent a C atom. H omitted on C. Included on functional groups. Multiple bonds indicated. Double line is double bond; triple line is triple bond. Heteroatoms written with required hydrogens.

37. Tro's Introductory Chemistry, Chapter 18 37 Functional Groups Other organic compounds are hydrocarbons in which functional groups have been substituted for hydrogens. A functional group is a group of atoms that show a characteristic influence on the properties of the molecule. Generally, the reactions that a compound will perform are determined by what functional groups it has. Since the kind of hydrocarbon chain is irrelevant to the reactions, it may be indicated by the general symbol R.

38. Tro's Introductory Chemistry, Chapter 18 38 Functional Groups, Continued

39. Alcohols R—OH. Ethanol = CH3CH2OH. Grain alcohol = fermentation of sugars. Alcoholic beverages. Proof number = 2x percentage of alcohol. Gasohol. Isopropyl alcohol = (CH3)2CHOH. 2-propanol. Rubbing alcohol. Poisonous. Methanol = CH3OH. Wood alcohol = thermolysis of wood. Paint solvent. Poisonous.

40. 40 Naming Alcohols Find the main chain that contains OH. Unless C=O present. Number main chain from end closest to OH. Give base name -ol ending and place number of C on chain where OH attached in front. CH3CH2CH2CH2CH2OH

41. Tro's Introductory Chemistry, Chapter 18 41 Ethers R–O–R. Ether = diethyl ether = CH3CH2OCH2CH3. Anesthetic. To name ethers, name each alkyl group attached to the O, then add the word ether to the end.

42. Tro's Introductory Chemistry, Chapter 18 42 Aldehydes and Ketones Contain the carbonyl group. Aldehydes = at least 1 side H. Ketones = both sides R groups. Many aldehydes and ketones have pleasant tastes and aromas. Some are pheromones. Formaldehyde = H2C=O. Pungent gas. Formalin = a preservative. Wood smoke, carcinogenic. Acetone = CH3C(=O)CH3. Nail-polish remover.

43. Tro's Introductory Chemistry, Chapter 18 43 Aldehyde Odors and Flavors Butanal = butter. Vanillin = vanilla. Benzaldehyde = almonds. Cinnamaldehyde = cinnamon.

44. Tro's Introductory Chemistry, Chapter 18 44 Ketone Odors and Flavors Acetophenone = pistachio. Carvone = spearmint. Ionone = raspberries. Muscone = musk.

45. Tro's Introductory Chemistry, Chapter 18 45 Naming Aldehydes and Ketone Make part of main chain. Number from end closest to carbonyl. Precedence over OH group. For aldehyde, change ending to -al. Always position 1, no number necessary. For ketone, change ending to -one. Indicate position on chain with number in front of base name.

46. Tro's Introductory Chemistry, Chapter 18 46 Carboxylic Acids RCOOH. Sour tasting. Weak acids. Citric acid. Found in citrus fruit. Ethanoic acid = acetic acid. Vinegar. Methanoic acid = formic acid. Insect bites and stings.

47. Tro's Introductory Chemistry, Chapter 18 47 Esters R–COO–R. Sweet odor. Made by reacting carboxylic acid with an alcohol. RaCOOH + RbOH ? RaCOORb + H2O Name alkyl group from alcohol, then acid name with -ate ending. Precedence over carbonyls, but not carboxylic acid. Number from end with ester group.

48. Tro's Introductory Chemistry, Chapter 18 48 Amines N containing organic molecules. Very bad smelling. Form when proteins decompose. Organic bases. Name alkyl groups attached to the N, then add -amine to the end.

49. Tro's Introductory Chemistry, Chapter 18 49 Amines Many amines are biologically active. Dopamine—a neurotransmitter. Epinephrine—an adrenal hormone. Pyridoxine—vitamin B6. Alkaloids are plant products that are alkaline and biologically active. Toxic. Coniine from hemlock. Cocaine from coca leaves. Nicotine from tobacco leaves. Mescaline from peyote cactus. Morphine from opium poppies.

50. Identify the Functional Groups in Each. CH3CH2COOCH3. (CH3CH2)2NH. CH3CHCHCH2CHO. 50 Tro's Introductory Chemistry, Chapter 18

51. Identify the Functional Groups in Each, Continued. CH3CH2COOCH3. (CH3CH2)2NH. CH3CHCHCH2CHO.