A Thistlewood 2007 Organic nomenclature educate net 2007

© A. Thistlewood 2007 What is it? • The systematic naming of an organic

© A. Thistlewood 2007 Naming straight-chain alkanes • Naming of straight chain alkanes (alkanes

© A. Thistlewood 2007 • Prefixes for alkanes that have 1 -4 carbons are

© A. Thistlewood 2007 Number of Carbons 1 2 Methane Ethane 3 4 5

© A. Thistlewood 2007 Naming branched alkanes • The nomenclature becomes more complex if

© A. Thistlewood 2007 • Next, determine the names of all substituents. Substituents are

© A. Thistlewood 2007 Try this one… a) • Which can be drawn as:

© A. Thistlewood 2007 Step 1 • Find the longest carbon chain in the

© A. Thistlewood 2007 © e-ducate. net 2007

© A. Thistlewood 2007 Step 2 • Number the parent chain. – The second

© A. Thistlewood 2007 8 7 6 2 1 4 3 5 1 2

© A. Thistlewood 2007 Step 3 • Name all the substituents. – You then

© A. Thistlewood 2007 Step 4 • Put the substituents in alphabetical order. –

© A. Thistlewood 2007 Step 5 • Locate the substituent on the parent change

© A. Thistlewood 2007 Your turn… • What is this? • And the structural

© A. Thistlewood 2007 • The prefixes di, tri, tetra etc. , used to

© A. Thistlewood 2007 A little harder… • Butanol… C 4 H 10 O

© A. Thistlewood 2007 A little harder… © e-ducate. net 2007

© A. Thistlewood 2007 Homework… • Draw and name all the possible structures with

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© A. Thistlewood 2007 What is it? • The systematic naming of an organic compound generally requires the identification and naming of a parent structure. • This name may then be modified by prefixes, infixes, and, in the case of a parent hydride, suffixes, which give the precise structural changes required to generate the actual compound from the parent structure. © e-ducate. net 2007

© A. Thistlewood 2007 Naming straight-chain alkanes • Naming of straight chain alkanes (alkanes that do not branch) is a straightforward process. • To give an alkane a name, a prefix indicating the number of carbons in the molecule is added to the suffix ane, identifying both the kind of molecule (an alkane) and how many carbons the molecule has (the prefix). • The name pentane, for example, tells you that the molecule is an alkane (thus the ane ending) and that it has five carbons (pent indicates five). © e-ducate. net 2007

© A. Thistlewood 2007 • Prefixes for alkanes that have 1 -4 carbons are rooted historically. • These are methane, propane, and butane, respectively. • On the other hand, for 5 carbons and up a prefix derived from greek is given. (An easy way to remember the first four names is the anagram Mary eats peanut butter, standing for methane, propane, butane). • Learning the prefixes for up to twelve carbons is a good idea. © e-ducate. net 2007

© A. Thistlewood 2007 Number of Carbons 1 2 Methane Ethane 3 4 5 6 7 8 9 10 11 12 Propane Butane Pentane Hexane Heptane Octane Nonane Decane Undecane Dodecane © e-ducate. net 2007 Prefix Structure CH 4 CH 3 CH 2 CH 3(CH 2)3 CH 3(CH 2)4 CH 3(CH 2)5 CH 3(CH 2)6 CH 3(CH 2)7 CH 3(CH 2)8 CH 3(CH 2)9 CH 3(CH 2)10 CH 3

© A. Thistlewood 2007 Naming branched alkanes • The nomenclature becomes more complex if the alkane branches. In such a case, there are several rules that you must follow to give the alkane the correct name. • Find the longest chain of carbons in the molecule. The number of carbons in the longest chain becomes the parent name. • After finding the parent chain, you number the parent chain starting with the end nearest the first substituent (a substituent is any fragment that juts off the main © e-ducate. net 2007 chain).

© A. Thistlewood 2007 • Next, determine the names of all substituents. Substituents are named as if the piece were a separate molecule, except that the suffix of yl is used rather than ane. • Thus, a two-carbon substituent would be an ethyl substituent (not an ethane substituent). • Put the substituents in alphabetical order (ie. ethyl before methyl) in front of the parent name. • Next, identify the positions of all substituents in the name by placing the carbon number where the substituent attaches to the parent chain in front of it. For example, 2© e-ducate. net 2007 methylheptane indicates that a methyl

© A. Thistlewood 2007 Step 1 • Find the longest carbon chain in the molecule. – First, begin by finding the parent chain in the molecule--that is, the longest possible chain of connecting carbons. – Note that the parent chain is not necessarily the chain that simply follows from left to right. – For example, if you were to count the number of carbons directly from left to right in this molecule you would get 7 carbons. This is not the parent chain, however! – If you start at the left and then count up where the molecule branches, you find that there are 8 © e-ducate. net 2007

© A. Thistlewood 2007 Step 2 • Number the parent chain. – The second step is to number the carbons in the parent chain starting at the end closest to the first substituent. – It is important to number the molecule from the correct end (in other words, in this example do you number the alkane from right to left or left to right). – Following this rule, on this molecule you number from right to left, as the 2 -carbon substituent is closer to that end. © e-ducate. net 2007

© A. Thistlewood 2007 Step 3 • Name all the substituents. – You then identify the names of the substituents. – In this case, the only substituent is a 2 carbon group at the number 4 carbon. – This is an ethyl group. 4 © e-ducate. net 2007

© A. Thistlewood 2007 Step 4 • Put the substituents in alphabetical order. – The next step is to put the substituents in alphabetical order (ie. ethyl before methyl) but since there is only one substituent this is unnecessary. © e-ducate. net 2007

© A. Thistlewood 2007 Step 5 • Locate the substituent on the parent change by giving it a number. – Thus, the proper nomenclature of this alkane is 4 -ethyloctane. – Note that a dash is used to separate the number from the substituent. © e-ducate. net 2007

© A. Thistlewood 2007 • The prefixes di, tri, tetra etc. , used to designate several groups of the same kind, are not considered when putting the substituents in alphabetical order. Number of same groups Prefix 1 mono 2 di 3 tri 4 tetra © e-ducate. net 2007

© A. Thistlewood 2007 Homework… • Draw and name all the possible structures with the formula: 1. C 3 H 7 Br (Br = bromo) 2. C 5 H 12 • Draw the following compounds: 1. 3 -ethyl-2, 4 -dimethylheptane 2. 2, 2, 4 -trimethylpentane 3. 4 -ethyl-3, 5 -dimethylheptane © e-ducate. net 2007