Unit 3- Organic Chemistry

Transcription

1 ` Unit 3- Organic Chemistry Lesson 1 Introduction to Organic Chemistry Feb 15 8:58 PM 1

2 Your First Mission Drawing upon your own chemical knowledge and everyday life, come up with the names of five compounds which you think are organic. Feb 15 8:59 PM 2

3 Organic Chemistry Pull down the molecule structures to identify the importance of each molecule. Organic molecules are important for life. Octane Glucose Nylon Ampicillin Fuel source for combustion engines. Fuel source for living cells. Polymer plastic for consumer products. Antibiotic agent. Carbon ydrogen Nitrogen Oxygen Organic chemistry. 3

4 What is organic chemistry? The study of molecular compounds containing carbon and hydrogen atoms. ex. C 4 C 3 O C 3 N 2 Properties of organic compounds result from the covalent bonds within their molecules Feb 15 8:59 PM 4

5 Origins of Organic Chemistry Swedish chemist Jons Jacob Berzelius Classified compounds in 2 categories 1)Organic -obtained from living organisms - most chemists believed organics could only be synthesized in living organisms thus the theory vitalism 2)Inorganic -obtained from mineral sources (non-living). Feb 15 9:06 PM 5

6 Origins of Organic Chemistry -German chemist Friedrich Wohler discovered that organic compounds could be synthesized from inorganic compounds. -Performed experiment with ammonium cyanate to synthesize urea (found in urine of living creatures). N 4 OCN (aq) (N 2 ) 2 CO (s) Feb 15 9:05 PM 6

7 -Acetic acid, C 3 COO; Sucrose, C O 11, as well as many others were and are synthesized. Feb 15 9:05 PM 7

8 Uniqueness of Carbon 1. Forms 4 bonds with other atoms Feb 15 9:04 PM 8

9 2. Bond together to form chains, rings, spheres, sheets and tubes of almost any size Feb 15 9:00 PM 9

10 3. Ability to form single, double or triple covalent bonds Feb 15 9:02 PM 10

11 Is this why we have so many organic compounds? YES! These unique properties explain why the number of known compounds of carbon far exceed the number of compounds of all other elements combined Today, over 98% of all known compounds are organic. Feb 15 9:03 PM 11

12 Comparing Inorganic & Organic Compounds Organic Compounds covalent bonding (share electrons) lower melting do not conduct electricity Inorganic Compounds mainly ionic bonding (transfer electrons) higher melting conduct electricity Feb 15 9:03 PM 12

13 Natural Sources Organic Compounds 1) Carbonized organic matter extracted from fossil fuels (once living matter) ex: coal, oil, and natural gas 2)From plants and animals (living organisms) Ex penicillin from mold ASA from the bark of a willow tree Feb 15 8:56 PM 13

14 Inorganic can be extracted from mineral sources (non living). Synthetic organic compounds such as gasoline, solvents, polyesters, synthetic sweeteners, artificial flavors (vanilla flavor), and medicines (antibiotics, aspirin, heart drugs) have been invented by chemists and engineers. These are copies of the natural products produced by plants and animals. Feb 15 8:55 PM 14

15 Two Classes of Compounds 1) Organic Compounds are compounds that have a combination of carbon and hydrogen Ex : C 4 C 3 O C 3 N 2 Feb 15 8:55 PM 15

16 2) Inorganic Compounds are compounds that have either carbon or hydrogen. They contained ionic bonds. Examples carbon oxides - CO x carbonate ion - CO 3 2- bicarbonate ion - CO 3 - cyanide ion - CN - thiocyanate ion - SCN - carbides - SiC EX: CO 2, CO Feb 15 8:55 PM 16

17 TWO CLASSES OF ORGANIC COMPOUNDS 1)ydrocarbons Organic compounds that contain only carbon and hydrogen atoms (Ex: methane, C 4 ). 2) ydrocarbon derivatives Organic compounds in which one or more hydrogen atoms are replaced by another nonmetallic atom (Ex: bromomethane, C 3 Br). Feb 15 8:13 PM 17

18 Feb 15 8:13 PM 18

19 Aliphatics organic compounds with chain or cyclic (rings) structures of single, double or triple bonds Feb 15 7:36 PM 19

20 Aromatic are organic compounds with a special group of six carbons ring known as the benzene ring. Feb 15 7:36 PM 20

21 Classifying Organic Compounds are separated into families and classified according to functional groups. These groups, the sites where reactions usually take place, help explain the many chemical properties of organic compounds. Functional Group is the characteristic arrangement of atoms within a molecule that determines the most important chemical and physical properties of the compound. Feb 15 7:35 PM 21

22 FAMILYFUNCTIONAL GROUP Alkane C C Alkene C = C Alkyne C C Aromatic (Benzene) Feb 15 7:34 PM 22

23 Alkanes (C n 2n+2 ) ydrocarbons that have only single covalent carbon-tocarbon bonds General Formula: C n 2n+2 Continuous Chain Alkanes alkanes containing any number of carbon atoms a straight chain Feb 15 7:33 PM 23

24 Naming Alkanes Ex1: What is the name of a compound with the molecular formula C 4 C Feb 15 7:32 PM 24

25 Naming Continuous Chain Alkanes Step 1 Use prefix as the first syllable to indicate the number of carbon atoms in the molecule [These prefixes are used in naming all organic compounds] Feb 15 7:31 PM 25

26 IUPAC Prefix System Number of Carbons Prefix 1 meth 2 eth 3 prop 4 but 5 pent 6 hex 7 hept 8 oct 9 non 10 dec Feb 15 7:30 PM 26

27 Step 2 Next, use the ending - ane to indicate single bonded carbon atoms Feb 15 7:30 PM 27

28 Therefore: C 4 Since 1 Carbon, we use Meth Since alkane, we use the ending ane Therefore, we have C 4, which is Methane!!! Feb 15 7:28 PM 28

29 Ex2: Name the compounds A. C 3 8 C C C propane Apr 12 9:21 AM 29

30 B. C 4 10 answer: butane C C C C Apr 10 4:58 PM 30

31 C. C 5 12 C C C C C answer: pentane Apr 10 4:57 PM 31

32 32 Feb 27 8:53 PM D. C 7 16 answer:eptane C C C C C C C C C C C C

33 Ex 3 : Name the compounds a) hexane b) c) C 8 18 octane decane Apr 10 5:13 PM 33

34 Jul 9 5:25 AM 34

35 Jul 9 5:25 AM 35

36 omologous Series a group of compounds that change by a constant increment in molecular structure from one compound in the series to the next compounds within a homologous series are known as homologs Feb 15 7:46 PM 36

37 Continuous chain alkanes are an example of a homologous series the constant increment in alkanes is the C 2 group The methane, ethane, propane and butane are an example of a homologous series. Feb 15 7:48 PM 37

38 Drawing Alkane Structures Each carbon will have 4 bonds Three types of structural diagrams 1. Complete all atoms and bonds in a molecule are shown Feb 15 7:56 PM 38

39 2. Condensed C- bonds are omitted but C-C bonds are shown For example, the chemical formula of C 4 10 can be represented as: (dashes are optional) or Feb 15 7:56 PM 39

40 Line each end of a line segment represents a carbon atom; hydrogen atoms are not shown Feb 15 7:57 PM 40

41 Ex 4:Draw all the structure diagrams for the following alkanes: A) C 7 16 Feb 15 8:03 PM 41

42 B) C 5 12 Feb 15 7:58 PM 42

43 Structural formulas show the bonds in a molecule, but they cannot represent molecules three dimensionally. Notice that a carbon "skeleton" is not perfectly straight, but zigzagged. Each carbon atom is bonded to four other atoms. VSEPR theory predict that each of the single bonds involving carbon points to a corner of a tetrahedron to give bond angles of about A really compact way of representing this structure is to use a line structural diagram. Apr 10 7:34 PM 43

44 Naming Branched Chain Alkanes branch an atom or group of atoms that can take the place of a hydrogen atom on the main carbon chain of a hydrocarbon molecule alkyl group a hydrocarbon branch that can be one o more carbons long It has one less hydrogen atom than a corresponding alkane named by removing ane ending and adding yl General Formula: C n 2n+1. Apr 10 7:43 PM 44

45 Alkyl groups are examples of substituents: atoms or groups of atoms that replace a hydrogen atom on a chain or ring of carbon atoms. Branched chain alkane alkane with one or more alkyl groups. Like the highway has roads branching off! Examples of branches: methyl: C 3 ethyl: C 2 5 or C 2 C 3 propyl: C 3 7 or C 2 C 2 C 3 butyl: C 4 9 or C 2 C 2 C 2 C 3 pentyl: C 5 11 or C 2 C 2 C 2 C 2 C 3 Apr 10 7:55 PM 45

46 Ex 5: Write a IUPAC name to represent this structural formula Apr 12 11:50 AM 46

47 Solution: 1. Begin by locating the longest continuous chain of carbon atoms. The longest chain is seven carbon atoms long, so the parent chain is heptane Feb 15 8:18 PM 47

48 2. Assign number "1" to the carbon at the end to which branching is closest. Since, branching is closest to the right side, the parent chain is numbered sequentially from right Feb 15 8:30 PM 48

49 3. Identify the alkyl groups. There are two: a methyl at carbon #3, and an ethyl at carbon #4. Feb 15 8:31 PM 49

50 4. If an alkyl group occurs more than once, use a Latin prefix to indicate the number present. The Latin prefixes are di = 2, tri = 3, tetra = 4, penta = 5, and so on. - e.g. two methyl groups would be represented as dimethyl 5. Use a number to indicate the location of each alkyl group on the parent chain. 6. Build the name of the branched alkane. 4-ethyl-3-methylheptane Feb 15 8:22 PM 50

51 Ex 6: Give the name for the following: Apr 12 11:50 AM 51

52 Drawing Structural Formulas for Branched Alkanes 1. Draw the parent chain. 2. Add the alkyl groups (substituents). 3. Make sure each carbon atom has an octet (e.g. four single covalent bonds). Feb 15 8:33 PM 52

53 Ex 7: Draw the structural formula for 3 ethyl 2,4 dimethylhexane. Answer The parent chain is hexane. Add methyl groups to carbon atoms 2 and 4 in the parent chain. Apr 10 8:08 PM 53

54 Add the ethyl group to carbon 3 Final Answer: Or Apr 10 8:10 PM 54

55 Ex 8: use notebook Draw structures to represent the following: (a) 2,2,4-trimethylpentane (b) 3-methylheptane Apr 12 11:52 AM 55

56 (c) 3-ethylhexane (d) 3-ethyl-2-methyl-4-propylnonane Apr 10 8:23 PM 56

57 (e) 2,3-dimethylhexane (f) 4-methylheptane Apr 10 8:23 PM 57

58 Condensed Structural Formulas for Branched Alkanes Method 1: Draw a condensed parent chain and draw lines to the alkyl substituents. Method 2: Draw a condensed parent chain and write the formulas for the alkyl substituents in parentheses Apr 10 8:29 PM 58

59 Cycloalkanes (C n 2n ) hydrocarbons which are arranged in a closed ring all c-c bonds are single bonds Feb 15 8:37 PM 59

60 Ex 9: Draw the full structural formula, condensed structural formula, and line drawing for cyclobutane. Apr 10 8:41 PM 60

61 Naming Cycloalkanes 1. Count the number of carbon atoms in the ring. 2. Name the structure the same as naming alkane but add the prefix cyclo to the alkane name. Ex 10: Name this compound. Apr 10 8:42 PM 61

62 Ex11: Name these compounds. cyclopropane cyclobutane cyclopentane cyclohexane Feb 15 9:07 PM 62

63 Physical Properties of Alkanes 1. Boiling Point relatively low melting and boiling points compared to inorganic compounds of similar size. (why? They have weak intermolecular force (LDF) holds them together hydrocarbons are nonpolar) generally, as the number of carbons atoms in a pure hydrocarbon increases, there is an increase in boiling and melting points ALKANES BOILING POINT number of electrons ethane, C propane,c butane,c pentane, C Apr 10 9:00 PM 63

64 2. Solubility: refers to the ability of a substance to dissolve in a particular solvent. Alkanes are non polar and are soluble in non polar solvents only. Q1. Why does alcohol dissolve in water? Water is polar. It will dissolve polar compounds. Alcohol is polar. ie: methanol, C 3 O Q2. Why does oil not dissolve in water? Oil is a pure hydrocarbon and like other pure hydrocarbons it is nonpolar. It will not dissolve in polar water. A common nonpolar solvent used to dissolve some hydrocarbons is carbon tetrachloride (CCl 4 ). Apr 10 9:04 PM 64

65 3. Rotation occurs around the single C-C bonds 4. The term saturated refers to organic compounds, which contain single carbon-to-carbon bonds Feb 15 8:46 PM 65

66 Structural Isomerism - compounds that have the same molecular formula but different structures Ex11: Draw the structural isomers of C butane methylpropane Apr 12 11:54 AM 66

67 Ex 12: Draw the structural isomers ofc 6 14 (5 structural isomers) Apr 10 9:14 PM 67

68 May 11 9:54 AM 68