Chapter 10 Introduction to Organic Chemistry: Alkanes. Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition

Transcription

1 1 hapter 10 Introduction to Organic hemistry: Alkanes

2 Organic hemistry and Organic ompounds 2 An organic compound is a compound made from carbon atoms has one or more atoms has many atoms may also contain O, S, N, and halogens usually has carbon written first Typical organic compounds have covalent bonds have low melting points have low boiling points are flammable most are not soluble in water

3 Organic vs. Inorganic ompounds 3 Propane, 3 8, is an organic compound used as a fuel. Nal, salt, is an inorganic compound composed of Na + and l ions.

4 4 omparing Organic and Inorganic ompounds Why is propane 3 8 organic, but Nal is not?

5 Learning heck 5 Identify each characteristic as most typical of compounds that are inorganic or organic. A. as a high melting point B. Is not soluble in water. as the formula D. as the formula Mgl 2 E. Burns easily in air F. as covalent bonds

6 Solution 6 Identify each characteristic as most typical of compounds that are inorganic or organic. A. as a high melting point inorganic B. Is not soluble in water organic. as the formula organic D. as the formula Mgl 2 inorganic E. Burns easily in air organic F. as covalent bonds organic

7 Bonding in Organic ompounds 7 Bonding in organic compounds: carbon has 4 valence electrons and hydrogen has only carbon achieves an octet by forming four bonds, with each line representing 2 electrons 4 methane

8 Tetrahedral Structure of arbon 4 8 arbon atom with four single, covalent bonds has a tetrahedral shape. Methane is represented using different models: (a) tetrahedron (b) ball-and-stick model (c) space-filling model (d) expanded structural formula

9 Tetrahedral Structure of arbon In ethane, each carbon forms covalent bonds to another carbon and three hydrogen atoms each carbon atom retains its tetrahedral shape Ethane, 3 3

10 Tetrahedral Structure of arbon In molecules with two or more carbon atoms, each carbon atom with four single bonds has a tetrahedral shape. Representations of ethane: (a) tetrahedral shape (each carbon) (b) ball-and-stick model (c) space-filling model (d) expanded structural formula

11 11 Organic ompounds formed by ydrogen and arbon: ydrocarbon ompounds. Alkanes Alkanes are organic molecules containing primarily single bonds commonly used as fuels for heaters and cooktops whose names end in ane named by using the number of carbon atoms connected in a continuous chain

12 Expanded, ondensed, and Skeletal Structures 12 General Formula of exane: 6 14 An organic molecule can be represented in several ways: a molecular formula a ball-and-stick model an expanded structural formula a condensed structural formula a skeletal formula

13 ondensed Structural Formulas 13 In a condensed structural formula, each carbon atom and its attached hydrogen atoms are written as a group a subscript indicates the number of hydrogen atoms bonded to each carbon atom carbon atoms are represented in a straight line Example: butane Expanded view Expanded view = 3 = 2 ondensed view ondensed view

14 14 Isomers Isomers are compounds that have the same molecular formula with different structural arrangements Since atoms can be bonded in different orders, the general molecular formula often applies to different compounds (Example 4 10 isomers). Therefore organic compounds are studied by using their structural formula instead of their general molecular formula

15 The Skeletal Formula 15 Due to the tetrahedral shape of each carbon atom, the carbon chain shows a zigzag pattern. Example: Butane can be written as: arbon chains can be written in several chain conformations: Butane can be written as:

16 The Skeletal Formula 16 The Skeletal Structural Formula is widely used when representing cyclic structures and more complex molecular structures. Example: holesterol

17 IUPA Naming of the First Ten Alkanes (using their condensed structural formula) 17

18 Learning heck 18 Based on the expanded structural formula: 1. What is the molecular formula? 2. What is the condensed structural formula? 3. What is the skeletal structural formula? 4. What is the name?

19 Solution 19 Based on the expanded structural formula: 1. What is the molecular formula? What is the condensed structural formula? What is the skeletal structural formula? 4. What is the name? Pentane

20 Learning heck 20 Write the condensed structural formula for A. ethane Write the condensed and skeletal structural formula for B. heptane

21 Solution 21 Write the condensed structural formula for A. ethane 3 3 Write the condensed and skeletal structural formula for B. heptane

22 Substituents or Attachments to the arbon hain 22 Alkane with no substituent Alkanes with a substituent

23 Substituent Groups or Attachments 23 Substituents are atoms or groups of atoms attached to the carbon chain and include alkyl and halo groups: Alkyl groups are carbon branches attached to carbon chains named with yl ending named as methyl, ethyl, propyl and isopropyl alo substituents are halogens attached to the carbon chain (F, l, Br, I) named as fluoro, chloro, bromo, or iodo

24 Substituents and Alkyl Groups 24

25 25 Guide to Naming Alkanes with Substituents

26 26 Write IUPA Names for Alkanes with Substituents Give the IUPA name for the following compound: l Step 1 Write the alkane name of the longest chain of carbon atoms. The longest chain has five carbons, so it is a pentane l

27 27 Write IUPA Names for Alkanes with Substituents Step 2 Number the carbon atoms starting from the end nearer a substituent. l #3 #4 # #1 #2 3 Step 3 Give the location and name of each substituent (in alphabetical order) as a prefix to the name of the main chain: 2-chloro-3-methylpentane

28 Learning heck 28 Give the IUPA name for the following compound: Br 3 Br

29 Solution 29 Give the IUPA name for the following compound: Br 3 Br Step 1 Write the alkane name of the longest chain of carbon atoms. The longest chain has four carbons, butane. Br 3 Br

30 Solution 30 Step 2 Number the carbon atoms starting from the end nearer a substituent. Br See substituents shown in circles Br Step 3 Give the location and name of each substituent (in alphabetical order) as a prefix to the name of the main chain. 1,2-dibromo-3-methylbutane

31 Drawing Formulas for Alkanes 31 Draw the structure for 1-bromo-3,4-dimethylheptane heptane: 7-carbon chain methyl groups on carbon 3 and 4 bromine on carbon 1

32 Drawing Formulas for Alkanes 32 Draw the structure for 1-bromo-3,4-dimethylheptane heptane: 7-carbon chain methyl groups on carbon 3 and 4 bromine on carbon 1 Solution Br

33 Guide to Drawing Formulas for Alkanes 33

34 Learning heck 34 Draw the condensed structural formula for 3-bromo-1-chlorobutane.

35 35 Solution Draw the condensed structural formula for 3-bromo-1-chlorobutane. Step 1 Draw the main chain of carbon atoms. The longest chain in butane has four carbon atoms. Step 2 Number chain and place the substituents on the carbons indicated by the numbers bromo: Br goes on carbon 3 l Br 1-chloro: l goes on carbon 1

36 Solution 36 Draw the condensed structural formula for 3-bromo-1-chlorobutane. Step 3 Add hydrogen to complete four bonds to each carbon. (aution: ydrogen atoms are missing!!!!!) l Br l Br 3-bromo-1-chlorobutane

37 ycloalkanes 37 ycloalkanes are cyclic alkanes have two less hydrogen atoms 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 propane, 3 8 cyclopropane,

38 Formulas of ycloalkanes 38

39 Learning heck 39 onvert the following skeletal structures to condensed structural formulas. Give the IUPA name for each compound: A. B.

40 Solution 40 onvert the following skeletal structures to condensed structural formulas. Give the IUPA name for each compound: A. octane B. cyclopentane

41 Learning heck 41 Name the following alkanes: A B D.

42 Solution 42 Name the following alkanes: A butane B. cyclopropane octane D. cyclohexane

43 Naming ycloalkanes with Substituents 43 Give the IUPA name for the following cycloalkane. 2 3 Step 1 Write the alkane name of the longest chain of carbon atoms. The longest chain is a six-member ring, cyclohexane. 2 3

44 Solution 44 Step 2 Number the carbon atoms starting from the end nearer a substituent Step 3 Give the location and name of each substituent (in alphabetical order) as a prefix to the name of the main chain. For cycloalkanes with just one substituent, there is no need to give the location of the substituent: ethylcyclohexane

45 Learning heck 45 Name each of the following cycloalkanes. A. 3 2 B. 3. l

46 Solution 46 Name each of the following cycloalkanes. 3 A. methylcyclopropane 2 3 B. ethylcyclobutane l. chlorocyclopentane

47 Example ycloalkane: When three branches are present Problem: Name this cycloalkane Parent chain = 6 (cyclohexane) Which way to number? 1, 1, 2 or 1, 2, 2 Branches? 3 branches: one iodo and two ethyl (use prefix di for the two ethyls) Alphabetize : 1, 2 diethyl 1 iodo Name: 1, 2- diethyl -1- iodocyclohexane

48 Properties of Alkanes: Physical States 48 Alkanes with one to four carbons are gases at room temperature and are widely used as heating fuels. Example; methane, ethane, propane, butane Butane has four carbons: Alkanes with five to eight carbons are highly volatile liquids at room temperature, making them useful in fuels such as gasoline. Example: pentane, hexane, heptane, octane Octane has eight carbons: Alkanes with 9 17 carbons are liquids with higher boiling points and are found in motor oils, mineral oil, kerosene, diesel, and jet fuels. Decane has 10 carbons:

49 Properties of Alkanes: Solubility and Density 49 Alkanes are nonpolar insoluble in water less dense than water flammable in air Alkanes are insoluble in water The crude oil in oil spills floats on top of the water, forming a thin layer on the surface because it is less dense than water.

50 Some Uses of Alkanes 50 Alkanes with 18 or more carbon atoms have high molar masses are waxy solids at room temperature are used in waxy coatings of fruits and vegetables Propane is used as a fuel in barbeques

51 Some Uses of Alkanes 51 Alkane Mixtures in rude Oil An oil refinery turns crude oil into usable fuel, producing natural gas, gasoline, kerosene, lubricant oils, and asphalt.

52 Some Uses of Alkanes 52 Alkane Mixtures in rude Oil

53 Reactions of Alkanes: ombustion 53 Alkanes have strong bonds Alkanes react with oxygen gas to make carbon dioxide and water in combustion reactions Alkanes release energy when bonds are broken in combustion reactions 4 (g) + 2O 2 (g) O 2 (g) O(g) + energy ombustion reactions are exothermic

54 Learning heck 54 Write a balanced equation for the complete combustion of propane.

55 Solution 55 Unbalanced equation: O 2 O O Balance : O 2 3O O Balance : O 2 3O O Balance O: O 2 3O O (balanced)

56 Reactions of Alkanes: alogenation alogenation of alkanes and alkyl halides A hydrogen atom on the alkane or alkyl halide is replaced by one of the two atoms of the halogen molecule (X 2 = F 2, l 2, Br 2, or I 2 ). eat (Δ) or ultraviolet light (uv) needs to be present to make the reaction happen if neither is present, the reaction does not occur.

57 Example of alogenation of Alkanes Problem: What is the product of the above reaction? alogenation removes a hydrogen from the alkane and replaces it with a halogen 3-2 Br + Br

58 Functional Groups 58 In organic molecules, arbon atoms have with four bonds Most bonds are with and other atoms sometimes carbon bonds to O, N, S sometimes carbon bonds to halogens F, l, and Br 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 chain a way to classify families of organic compounds

59 Alkenes, Alkynes and Aromatic ompounds 59 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.

60 60 omparing Alkenes, Alkynes, and Aromatic ompounds

61 Learning heck 61 Identify the following compounds as alkane, alkene, alkyne or aromatic compound: A. E. B. F.. G. D..

62 Solution 62 Identify the following compounds as alkane, alkene, alkyne or aromatic compound: A. E. Aromatic Alkane B. F. Alkene Alkene. G. Alkyne Alkane D.. Alkane Aromatic

63 Alcohols, Thiols, and Ethers 63 An alcohol contains the hydroxyl ( O) functional group. Alcohol 3 2 O A thiol contains the thiol ( S) functional group. Thiol 3 2 S An ether contains an oxygen atom bonded to two carbon atoms ( O ) functional group. Ether 3 O 3

64 Aldehydes and Ketones 64 An aldehyde contains a carbonyl group (=O), which is a carbon atom with a double bond to an oxygen atom. The carbonyl carbon is attached to a hydrogen. Aldehyde O // 3 In a ketone, the carbon of the carbonyl group (=O) is attached to two carbon atoms. Ketone O // 3 3

65 65 arboxylic Acids and Esters arboxylic acids contain the carboxyl group, ( OO) which is a carbonyl group attached to a hydroxyl group: arboxylic acid O // 3 O An ester contains the carboxyl group between carbon atoms ( OO- 3 ) Ester O // 3 O 3

66 66 Amines Amines have a functional group that contains a nitrogen atom are derivatives of ammonia, N 3, in which one, two, or three hydrogen atoms are replaced with carbons 3 N 2 Amine 3 N 3 3 / 3 N 3

67 Amides 67 Amides have an amine group instead of an O group on the carbonyl carbon O N O // 3 N 2 are an important biological functional group, the simplest amide being urea 2 N Amide O N 2 O // N 2 N 2

68 lassification of Organic ompounds 68

69 Learning heck 69 lassify each of the following as an alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide. A. B.. D. E.

70 Solution 70 lassify each of the following as an alcohol, ether, aldehyde, ketone, carboxylic acid, ester, amine, or amide. A. Alcohol B. Ether. Amine D. arboxylic Acid E. Ester