Isomerism CH 4 C 2 H 6 C 3 H 8 C 4 H 10 C 5 H 12. Constitutional isomers...

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1 Isomerism onstitutional isomers...

2 3 8 Positional isomers... Functional isomers... ow many constitutional isomers are there for the formula 4 8?

3 arbon atoms are often classified as primary (1 ), secondary (2 ), tertiary (3 ), and quaternary (4 )... methane Label the carbon atoms in the following molecule as 1, 2, 3, or 4. emember, these labels only pertain to carbon atoms with four single bonds

4 This terminology also applies to amines... N N ammonia N N N and amides... 3 N 3 4

5 Unsaturated arbon lassification... alkynyl carbons alkenyl protons aryl protons and carbons alkynyl hydrogen alkenyl carbons For more examples, see the textbook, page 23. Until you hear otherwise, the terms primary, secondary, tertiary and quaternary shall apply to saturated carbons. So, if asked for a molecule that contains only 3 carbons, benzene would not be a correct answer. 5

6 alkenes alkanes alkynes Functional Groups: eactive centers that contain heteroatoms or multiple carboncarbon bonds. eteroatom: atoms other than carbon or hydrogen. Typically N,, Si, P, S, Se, F, l, Br, I. multiple carbon-carbon bonds: unsaturation. N Br 6

7 The Functional Groups (Table 1.1 page 4) Structure ondensed Structure Name Nomenclature suffix 2 or arboxylic acid -oic acid S S 3 Sulf onic acid -sulfonic acid 2 or Ester -oate 7

8 l l Acid chloride -oyl chloride N () N 2 () 2 Amide -amide () N N Nitrile -nitrile Aldehyde -al Ketone -one 8

9 Alcohol -ol S S Thiol -thiol N N 2 Amine -amine Alkene -ene Alkyne -yne Ether N/A 9

10 Alcohol -ol S S Thiol -thiol N N 2 Amine -amine Alkene -ene Alkyne -yne Ether N/A 10

11 other common functional groups Arene N/A Phenol N/A S Sulf ide N/A S S S 2 Disulfide N/A S S Sulf oxide N/A N N 2 Nitro N/A 11

12 Things to watch for... common structural elements. Both of these contain the hydroxyl group(-) but they represent different functional groups. N Both of these contain the carbonyl group(=, pronounced carbon-eel group) but they represent different functional groups. IMPTANT: the carbonyl group by itself is not a functional group. It is part of many functional groups depending on what is attached to it. 12

13 The "open" bond in these structures is attached to a carbon Ketone 3 Ketone 3 Not a ketone and, with the exception of alkene/alkyne/arene, this carbon is usually not part of another functional group Ether 3 3 Ether Not an ether

14 rganic Nomenclature Systematic IUPA Nomenclature ompound names have four fields. First field Second field Third field Fourth field substituents compound root saturation index principal functional group 14

15 ompound oot Second Field The compound root name is based on the number of carbon atoms in the longest continuous chain or ring. n n 2n+2 alkane 1 4 meth-ane eth-ane prop-ane 4 3 ( 2 ) 2 3 but-ane 5 3 ( 2 ) 3 3 pent-ane 6 3 ( 2 ) 4 3 hex-ane 7 3 ( 2 ) 5 3 hept-ane 8 3 ( 2 ) 6 3 oct-ane 9 3 ( 2 ) 7 3 non-ane 10 3 ( 2 ) 8 3 dec-ane For cyclic molecules, the prefix cyclo is added before the compound root prefix. 15

16 Saturation Index Third Field The presence of multiple bonds is indicated by ene (carbon-carbon double bonds) and/or yne (carbon-carbon triple bonds) in the third field of the name When a principal functional group is not present, number the chain to give the multiple bond the lowest number. If there are multiple multiple bonds, add the prefix di, tri, tetra, etc to indicate the number of double or triple bonds in the molecule and give a number to indicate its position. 16

17 Substituents First Field 5-chloro-1-hexene (or 5-chlorohex-1-ene) 4,5-dichloro-5-fluoro-1-hexene (or 4,5-dichloro-5-fluorohex-1-ene) 17

18 Principal Functional Groups Forth Field Functional Group arboxylic acid Sulfonic acid Ester* Acid hloride Amide* Nitrile Aldehyde Ketone Alcohol (including phenol) Thiol Amine Suffix -oic acid -sulfonic acid -oate -oyl chloride -amide -nitrile -al -one -ol -thiol -amine Note that certain functional groups are never considered as a principal functional group and are always treated as a substituent. These include the halogens, ethers, and nitro 18 groups.

19 Principal Functional Groups Forth Field 5-chloro-1-hexen-3-ol (or 5-chlorohex-1-en-3-ol) 2-chloro-5-hexen-1-ol (or 2-chlorohex-5-en-1-ol) 2-chloro-4-hydroxy-5-hexenal (or 2-chloro-4-hydroxyhex-5-enal) Note that no number is necessary for principal functional groups that must be terminal because they include the first carbon atom of the main chain. 19

20 Substituent List Name Name Name - 3 methyl - 3 methoxy -F fluoro ethyl ethoxy -l chloro propyl propoxy -Br bromo butyl butoxy -I iodo etc. etc. -N 2 amino -( 3 ) 2 isopropyl -( 3 ) 2 isopropoxy -N 2 nitro - 2 ( 3 ) 2 isobutyl - 2 ( 3 ) 2 isobutoxy -N cyano - s-butyl - ( 3 ) 2 3 ( 3 ) 2 3 s-butoxy -( 3 ) 3 t-butyl -( 3 ) 3 t-butoxy - hydroxy phenyl phenoxy = oxo benzyl benzoxy -S mercapto 20

21 ther names you need to know... Benzene = Molecules with this substructure are treated as a class arenes. 3 N 2 2 toluene* aniline* phenol benzaldehyde benzoic acid *these are not IUPA names but common names that you should know. 21

22 Naming arbon-based Substituents methane methyl methyl group ethane ethyl ethyl group 22

23 n-propyl The n-propyl or propyl group. ("n" stands for normal i.e. straight chain) propane isopropyl The 2-propyl or isopropyl group. Notice that the only difference between n-propyl and isopropyl is the point of attachment. 23

24 The n-butyl or butyl group. n-butyl butane sec-butyl The 2-butyl, sec-butyl or s-butyl group. Again, notice that the only difference is the point of attachment. 24

25 3 3 3 isobutyl The isobutyl group. 3 3 isobutane tert-butyl The 2-methyl-2-propyl, tert-butyl or t-butyl group. 25

26 Aryl based Substituents Phenyl Ph or Benzyl Bn or benzylic 26

27 ommon Unsaturated Alkyl substituents 2 Vinyl or ethenyl "allylic" 2 Allyl or propenyl propenyl or isopropenyl (incorrect page 24) 2 Propargyl

28 Yet more substituents... "Acyl" substituents... "Formic acid" formyl 2 Benzyl "Acetic acid" acetyl Ph Benzoic acid Ph benzoyl N 4-acetylpyridine

29 Alkoxy substituents 3 Methanol 3 methoxy 3 2 Ethanol 3 2 ethoxy 3 methoxycyclopentane Phenol phenoxy

30 It's all Greek... n occasion, greek letters are used to indicate the position of an atom relative to a functional group... Br 2 " -bromoacetic acid" 2 N 2 3 An -amino acid. 2 3 An example of an -unsaturated ketone.

31 rganic Nomenclature Summary: 3 Br Br Br Br

32 Practice Substituents oot Unsaturations Functional Group 2 3 S Br