CHEMISTRY - TRO 4E CH.21 - ORGANIC CHEMISTRY.

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2 TOPI: ORGANI EMISTRY Organic hemistry is the study of carbon and the other common nonmetals it is connected to:,, &. Some organic molecules are made of just carbons and hydrogens and are aptly named. O A B N l D Page 2

3 TOPI: STRUTURAL FORMULAS Your typical organic molecule can be drawn in a few different ways. For example if you take a look at pentane, Structural Formula ondensed Formula Skeletal Formula EXAMPLE 1: Determine the molecular formula for the following organic compound. EXAMPLE 2: onvert the following structural formula into its condensed formula. 3 Page 3

4 PRATIE: STRUTURAL FORMULAS 1 EXAMPLE 1: Determine the molecular formula for the following organic compound. EXAMPLE 2: Determine the molecular formula for the following organic compound. O N O N Uracil (U) RNA EXAMPLE 3: onvert the following structural formula into the carbon skeleton formula, otherwise known as a kekulé structure. O O O N Page 4

5 TOPI: IRALITY A molecule is chiral when it possesses a carbon that has unique groups attached to it. This molecule is said to be non-superimposable. The mirror image of any chiral molecule is called an and together they are referred to as isomers or isomers. Br Br O 3 3 O mirror EXAMPLE 1: Identify the compound that possesses an asymmetric center. l 3 l O 2 3 l 3 F A B D Page 5

6 PRATIE: IRALITY 1 EXAMPLE 1: From the previous question draw the mirror image of the chiral molecule. EXAMPLE 2: Draw the mirror images for the following molecule. Mirror Method Inversion Method l O PRATIE: Draw the mirror images for the following molecule. Mirror Method Inversion Method Page 6

7 TOPI: OPTIAL ATIVITY We recently learned that a chiral molecule is one that possesses a carbon connected to four distinct groups. One key feature of chiral molecules is that they rotate plane polarized light. lockwise rotation = dextrorotatory (d) or (+) ounterclockwise rotation = levorotatory (l) or ( ) hiral Solution hiral Solution The names and degrees of rotation have nothing to do with the chirality of the compounds. EXAMPLE: Which of the following compounds would be optically active? O F Br l A B D Page 7

8 TOPI: YDROARBONS The term of hydrocarbon refers to compounds that contain only carbons and hydrogens. These compounds may possess single, double or triple bonds. arbons are meaning that when they are neutral they must make 4 bonds. Alkane Alkene Alkyne Benzene Alkane Prefixes The name of alkanes is based on the number of carbons in the compound. These alkane prefixes must be memorized in order to name more complex structures later on in the chapter. # of arbons Alkane Prefix # of arbons Alkane Prefix Page 8

9 Alkanes Alkanes are hydrocarbons that contain only single bonds. They are sometimes referred to simply as saturated hydrocarbons. Since all of the carbons are connected to 4 electron groups they all have an hybridization. Alkanes have a generic formula of. Ethane Propane EXAMPLE 1: Determine the formula and name of a hydrocarbon that contains only single bonds and 8 carbons. There is a direct relationship between an alkane s weight and it s measured boiling point. Generally, the the molecular weight of an alkane the higher its boiling point. Number of arbons Physical State Usage Up to 4 Gas ooking and eating 5 to 7 Volatile Liquids Gasoline and solvents 6 to 18 Liquids Gasoline 12 to 24 Liquids Jet Fuel 16 to 50 igh Boiling Liquids Diesel, heating oils and grease Over 50 Solids Petroleum jelly, waxes Page 9

10 Alkenes Alkenes are hydrocarbons that contain at least one double bond. They are sometimes referred to simply as unsaturated hydrocarbons. The double bonded carbons are connected to 3 electron groups and so have an hybridization. Alkenes and cycloalkanes have a generic formula of. Ethene Propene yclohexane EXAMPLE 2: Determine the formula and simplest name of a hydrocarbon that contains one double bond and 6 carbons. Page 10

11 Alkynes Alkynes are hydrocarbons that contain at least one triple bond. They are sometimes referred to simply as unsaturated hydrocarbons just like the alkenes. The triple bonded carbons are connected to 2 electron groups and so have an hybridization. Alkynes have a generic formula of. Ethyne Propyne EXAMPLE 3: Determine the formula and simplest name of a hydrocarbon that contains one triple bond and 9 carbons. Page 11

12 Aromatics Aromatic compounds have a benzene ring (66) as their major defining feature. Resonance Structures Resonance ybrid Benzene rings can be found in many everyday compounds from fossil fuels to even some vital medications. Page 12

13 TOPI: ALKYL GROUPS The removal of a hydrogen atom from an alkane compound creates an alkyl group. Remembering these alkyl groups are the first step in learning how to name organic compounds. Methane Methyl When you have a two carbon chain then the alkyl name will be Page 13

14 When you have a three carbon chain then the alkyl name will be or When you have four carbons then the alkyl names will be,, or Page 14

15 EXAMPLE: Based on your knowledge of chemical structures draw the three isomers of 512 (pentane). Page 15

16 TOPI: NAMING ALKANES When naming any alkane compound there is a set of rules you should follow to get the correct answer. 1. Find the longest carbon chain and assign a root name accordingly. If there is a tie between longest chains, choose the chain that gives substituents. Substituents are the groups that branch off the main chain and weren t counted as part of the main chain. 2. Number the chain from the end closest to a substituent. 3. Substituents will be named alphabetically and a number will accompany the location of their attachment. 4. If more than one of a similar alkyl group is present then we must use numerical prefixes to describe the number of them Page 16

17 PRATIE: NAMING ALKANES 1 EXAMPLE 1: Naming the following alkane compound. a) EXAMPLE 2: Naming the following alkane compound. b) EXAMPLE 3: Naming the following alkane compound. c ) Page 17

18 PRATIE: NAMING ALKANES 2 EXAMPLE 4: Determine the structure for the following alkane compound. 3, 4, 5-trimethyldecane EXAMPLE 5: Determine the structure for the following alkane compound. 4-tert-butyloctane EXAMPLE 6: Determine the structure for the following alkane compound. 1-bromo-2,3-dichlorocycloheptane Page 18

19 TOPI: NAMING ALKENES Naming an alkene is similar to naming an alkane with a few differences. 1. Find the longest carbon chain and change the ane ending to ene. If there is a tie between longest chains, choose the chain that gives substituents. 2. Number the chain from the end closest to the double bond and provide a number for its location. 3. Substituents will be named alphabetically and a number will accompany the location of their attachment. 4. If more than one of a similar alkyl group is present then we must use numerical prefixes to describe the number of them EXAMPLE 1: Naming the following alkene compound. Page 19

20 PRATIE: NAMING ALKENES 1 EXAMPLE 2: Naming the following alkene compound. EXAMPLE 3: Determine the structure for the following alkene compound. 5-bromo-4,4-dimethyl-2-heptene EXAMPLE 4: Determine the structure for the following alkene compound. 2, 5 octadiene EXAMPLE 5: Determine the structure for the following alkene compound. Trans 3 hexene Page 20

21 TOPI: NAMING ALKYNES Naming an alkyne is similar to naming an alkane with a few differences. 1. Find the longest carbon chain and change the ane ending to yne. If there is a tie between longest chains, choose the chain that gives substituents. 2. Number the chain from the end closest to the triple bond and provide a number for its location. 3. Substituents will be named alphabetically and a number will accompany the location of their attachment. 4. If more than one of a similar alkyl group is present then we must use numerical prefixes to describe the number of them EXAMPLE 1: Naming the following alkyne compound. EXAMPLE 2: Provide the structural formula from the following alkyne name. 4 phenyl 2 nonyne Page 21

22 TOPI: ALKANE REATIONS Alkanes are also referred to as, which is derived from Latin meaning little affinity. This explains their very low reactivity. Alkanes in general undergo only two main types of reactions. a) b) Page 22

23 TOPI: FREE RADIAL AIN REATION As previously stated, alkanes are almost completely unreactive. And one of the two reactions it undergoes is free-radical halogenation. Under this reaction a on a carbon is replaced by a. The Radical hain Reaction Alkanes will react with diatomic halogens in the presence of. Initiation: (A stable compound undergoes homolytic cleavage: 0 free radicals 2 free radicals) Propagation: (The radical reacts with a stable compound to create a new radical and new stable compound.) Termination: (Two radicals join to create a stable compound: 2 free radicals 0 free radicals) Page 23

24 PRATIE: FREE RADIAL AIN REATION 1 EXAMPLE 1: Determine the major product(s) of the following reaction Br 2 eat or Light EXAMPLE 2: Determine the major product(s) of the following reaction l 2 eat or Light Page 24

25 TOPI: ALOGENATION Alkenes and alkynes undergo addition reactions in which elements add across their bonds to create new bonds. Under alogenation, halogens are added to pi bond. EXAMPLE 1: Determine the major product from the following alogenation reaction. 3 = 2 + l 2 EXAMPLE 2: Determine the major product from the following alogenation reaction. + 2 moles Br 2 Page 25

26 TOPI: YDROGENATION ydrogenation can be seen as a reduction reaction in which hydrogens are added to pi bond. In General hemistry reduction is gaining, but in Organic hemistry reduction is thought of as gaining. EXAMPLE 1: Determine the major product from the following ydrogenation reaction. + 2 atalyst EXAMPLE 2: ow many moles of hydrogen would be needed to completely reduce the following compound? 3 3 Page 26

27 TOPI: YDROALOGENATION Under ydrohalogenation, a and a are added across a pi bond. 1) Follows Markovnikov s Rule a) ydrogen goes to the double bonded carbon with hydrogens. b) alogen goes to the double bonded carbon with hydrogens. EXAMPLE 1: Determine the major product from the following ydrohalogenation reaction l EXAMPLE 2: Determine the major product from the following ydrohalogenation reaction moles Br Page 27

28 TOPI: AROMATI REATIONS Although benzene rings have pi bonds like alkenes and alkynes, they cannot undergo addition reactions because they are much too stable. We often refer to benzene as an aromatic compound in order to describe its high level of stability. Instead of doing addition reactions benzene rings will under reactions in order to maintain their aromaticity. The two major types of Aromatic reactions we will investigate will be: 1. where a halogen is placed on benzene. + Br 2 FeBr 3 + l 2 Fel 3 Page 28

29 2. where an alkyl group is placed on benzene. + 3 l All 3 EXAMPLE 1: Determine the major product from the following Aromatic reaction. + Br AlBr 3 Page 29

30 TOPI: NOMENLATURE OF FUNTIONAL GROUPS Naming a compound with a functional group is similar to previous examples of naming we ve done. 1. Find the longest carbon chain and change the ane ending based on the functional group present. If there is a tie between longest chains, choose the chain that gives substituents. 2. Number the chain from the end closest to the functional group present and provide a number for its location. Some functional groups don t need their location numbered because they are terminal. 3. Substituents will be named alphabetically and a number will accompany the location of their attachment. 4. If more than one of a similar alkyl group is present then we must use numerical prefixes to describe the number of them lass arboxylic Acid Ester Aldehyde Ketone Alcohol Amine Alkene Alkyne Alkane Ether Suffix Name -oic acid -oate -al -one -ol -amine -ene -yne -ane ether Alkyl alide --- Page 30

31 PRATIE: NOMENLATURE OF FUNTIONAL GROUPS 1 EXAMPLE 1: Provide the name of the following alcohols and alkyl halides and state if they are primary, secondary or tertiary. O a) Br O b) l c) EXAMPLE 2: Provide the name of the following functionalized organic compounds. O a) 3O O b) O c) Page 31

32 PRATIE: NOMENLATURE OF FUNTIONAL GROUPS 2 EXAMPLE 3: Provide the name of the following functionalized organic compound. EXAMPLE 4: Provide the name of the following amines and state if they are primary, secondary or tertiary. N 2 a) b) N 2 3 EXAMPLE 5: Provide the name of the following ethers a) O 3 b) 3 2 O 2 3 Page 32

33 PRATIE: NOMENLATURE OF FUNTIONAL GROUPS 3 EXAMPLE 6: Provide the structure of the following aromatic hydrocarbons. p-ethyltoluene EXAMPLE 7: Provide the structure of the following aromatic hydrocarbons. m-bromobenzoic acid EXAMPLE 8: Provide the structure of the following aromatic hydrocarbons. 2,4,6-trimethylnitrobenzene Page 33

34 TOPI: ALOOL REATIONS Alcohols can be easily identified by the presence of the hydroxyl group. Because of the presence of this highly polarized group alcohols can be involved in many organic reactions. 1. Substitution Reactions under this reaction alcohols react with the hydrohalic acids of or to become alkyl halides. O Br 2. Elimination Reactions under this reaction under the presence of concentrated acids such as or an alcohol undergoes dehydration to form an alkene. O SO 4 3 Page 34

35 3. Oxidation Reactions An alcohol can be seen as an alkane that has undergone an initial oxidation. The alcohol can then continue to be oxidized to form either a(n) or. This is done with the strong oxidizing agent sodium dichromate, Na2r2O7 and the strong acid sulfuric acid, 2SO4. There is also an inverse relationship that can change our products back into their reactants O Na 2 r 2 O 7 2 SO 4 O Na 2 r 2 O 7 2 SO 4 O Na 2 r 2 O 7 2 SO 4 Page 35

36 TOPI: ARBOXYLI AID DERIVATIVE REATIONS Esters and amines are involved in reactions that deal with carboxylic acids. 1. Esterification Under this reaction a carboxylic acid reacts with an alcohol and undergoes a dehydration reaction in order to form an ester. O O O eat 2. Amide Formation Under this reaction a carboxylic acid reacts with an amine and undergoes a dehydration to reaction in order to form an amide. O 3 2 O N 3 eat Page 36