Naming for Chem 201 CH 4

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1 Naming for Chem 201 Functional groups are referred to as such because they function or react differently and give the molecule different properties. Here s a list of the groups you need to be able to name for the exam: Note that R stands for any random carbon chain. Functional Group Formula Suffix Carboxylic Acids -oic acid Esters -oate Amide *R can be H -amide Aldehyde -anal Ketone -one Alcohol Amine *R can be H Ether Alkene -ol -amine ether -ene Alkyne Alkyl halide -yne treated as a branch Alkane CH 4 Normally, you are taught the functional groups one by one. This is because the groups above are organized by priority (carboxylic acids are high priority and alkanes are low). However, for Chem201, you have only ever been tested on one group in a structure. The color coding above is to highlight the fact that the groups above have similar naming. -ane

2 Alkanes: All alkanes end in -ane and begin with a prefix (see table at right). The prefix tells you the number of carbons in the chain: butane C 4 H 10 octane C 8 H 18 methane CH 4 Prefix meth eth prop but pent hex hept oct non dec Number of Carbon atoms in the chain There are multiple ways to represent alkanes. So far I have used Lewis/Expanded structures: Lewis/Expanded Structure Molecular Formula C 8 H 18 Condensed Formula CH 3 (CH 2 ) 6 CH 3 Line/Skeletal Diagram The preferred method is the line/skeletal diagram. As we saw in lecture, carbon atoms form four bonds. Each vertex in the line diagram is a carbon. If it is already bonded to two carbons (such as carbons 2 through 7) it must have space for only 2 bonds and they must be C-H bonds. Therefore carbons 2-7 are CH 2 and carbons 1 and 8 are CH 3. methane ethane propane CH 4 - cannot be represented as a line diagram butane heptane octane

3 Branching: *For the rest of this guide, I will be using line diagrams because they are the FASTEST way to communicate organic chemistry. It is recommended you number the ends and points on the chain to follow along better! When alkanes are branched, we identify the longest chain and count from the side that gives the lowest number for the branch: = = = Whenever we have a branch, all we do is add the suffix -yl to the branch and indicate the carbon number where the branch is attached. This structure is called 2-methylhexane. Note that if we flip the structure 180 it still has the same name. If we curl up the line diagram it still has the same number of vertices and we can still count 6 carbons in the longest chain with the methyl group being on the second carbon. The number 2 is called the locant of that branch or group. 3-ethyl-4-methylhexane 3-methyl-4-propyloctane CH 3 CH 2 CH(CH 2 CH 3 )CH(CH 3 )CH 2 CH 3 CH 3 CH 2 CHCH 3 CH(CH 2 CH 2 CH 3 )(CH 2 ) 3 CH 3 In the condensed formula (given above), brackets are used to denote repeating units AND branches. If we have more than one branch, the branch gets a prefix: 3,4,5-trimethyloctane Do NOT get carried away with branches! Most likely you will get a linear chain or 1 branch (methyl or ethyl). Also, naming is only 1-2 marks on the entire exam. Line diagrams are another 1 mark and condensed formulas are 2 marks. Prefix (none) di tri tetra penta hexa hepta octa nona deca Number of Carbon atoms in the chain 1 (not used)

4 Haloalkanes are alkanes with a Halogen on them (e.g. F, Cl, Br or I) The halogen is treated as a branch and gets the name fluoro, chloro, bromo or iodo depending on the element. The halides are ordered alphabetically. 2-bromopropane 2,2-difluoropentane Constitutional Isomers are molecules with the same atoms but different bonding. It does not matter what functional group is present if the molecular formula is the same, the compounds are isomers. The following compounds are all constitutional isomers: octane or C 8 H 18 2,4-dimethylhexane or C 8 H 18 2,2,3-trimethylpentane or C 8 H 18 2,2,3,3-tetramethylbutane or C 8 H 18

5 The following functional groups are named similarly the ending is changed to reflect the position of the group: Functional Group Formula suffix Example Example Name Ketone -one 2-hexanone or hexan-2-one Alcohol -ol 2-butanol or butan-2-ol Alkene -ene (E)-2-pentene or (E)-pent-2-ene Alkyne -yne 1-heptyne or hept-1-yne Alkenes end in -ene and have a number to indicate the position of the double bond: prop-1-ene (E)-but-2-ene hex-3-ene You cannot rotate around a double bond and, because of this, the following pairs of structures are different: (E)-but-2-ene (E)-pent-2-ene (E)-hex-3-ene (E)-hept-3-ene (Z)-but-2-ene (Z)-pent-2-ene (Z)-hex-3-ene (Z)-hept-3-ene

6 When functional groups are present, the highest priority functional group is given the lowest number. In Chem201 profs. haven t mixed and matched multiple groups in a compound so this simply means the only functional group aside from an alkane is given the lowest number: 2,3-dimethylhex-3-ene 5,6-dimethylhept-2-ene 5,6-dimethylhept-2-ene Alkynes end in -yne and have a number to indicate the position of the triple bond: but-2-yne 4-methylpent-2-yne 4-methylhept-2-yne

7 Alcohols: have the suffix -ol and contain an OH group. The OH group can be referred to as a hydroxyl group. propan-1-ol propane-1,2-diol Ketones: have the suffix -one and contain a carbonyl group (RC(O)R). butan-2-one pentan-3-one hexan-2-one

8 The next set of compounds is named similarly because, typically they are the most important group on a small organic compound and are terminal meaning they are always position 1 (at the end of a molecule). Because of this, they typically don t need a locant (number identifying where the group is). The naming for amines and amides can get much more complex but I don t expect that in Chem 201. Functional Group Carboxylic Acids Formula Suffix Example Example Name -oic acid hexanoic acid Amide *R can be H -amide butanamide Aldehyde -anal propanal or Amine *R can be H -amine pentanamine Carboxylic Acids: Carboxylic Acids have an OH (hydroxyl) next to a CO (carbonyl) the combination of the two is called a carboxyl (COOH). Carboxylic acid names have the suffix oic acid. We always start numbering a carboxylic acid from the carbon attached to the two oxygen: butanoic acid pentanoic acid 3-methylhexanoic acid 4-methylpentanoic acid The other similarly named functional groups also number position 1 as the amine, aldehyde, etc. (if there are no other higher ranking groups)

9 Aldehydes: Aldehydes end in anal. They kind of look like ketones but they are at the ends of the molecule (terminal). Thus they too are always position one. We call them a separate functional group from ketones because they have different reactivity. butanal 2-methylbutanal 3-methylbutanal heptanal Amides: Amides are a carboxylic acid derivative composed of an NR 2 (amino group) next to a CO (carbonyl) the combination of the two is called an amide (CONR 2 ). Although you can have alkyl groups on the amide: N,N-dimethylbutanamide It is more likely you will see a straight chain connected to an NH 2 butanamide 2-methylbutanamide 3-methylbutanamide When naming amides we add the suffix amide. pentanamide Carboxylic acid names have the suffix oic acid. We always start numbering a carboxylic acid from the carbon attached to the two oxygen:

10 Amine: Amines (NR 3 ) can have H instead of R and are named similarly to amides. They have the suffix amine: propanamine butanamine hexanamine 2-methylhexan-1-amine 5-methylhexan-1-amine Note that the amine is on position 1. The naming becomes more interesting when we add more groups to the nitrogen: ethyl propyl amine methyl butyl amine methyl ethyl propyl amine Notice how there is an intentional space between the different chains it s a bit like there s more than one root. Both ester and ethers are molecules with two alkyl chains. They have a similar naming scheme (intentional space) to an amine: Functional Group Formula Suffix Example Example Name Esters -oate methyl butanoate Ether ether methyl butyl ether Ethers: Ethers can be named similar to amines with multiple chains: ethyl methyl ether ethyl ethyl ether or diethyl ether methyl propyl ether butyl propyl ether Note that the alkyl groups are listed simply in alphabetical order.

11 Esters: are a carboxylic acid derivative (they look like and can be made from a carboxylic acid). The root of an ester has the added suffix oate. Esters have two parts - the carbon attached to 2 oxygen atoms forms the root name: ethyl butanoate. The root is highlighted in red and has 4 carbons, therefore it is the butanoate. The alkyl (or alkane) group attached to the oxygen is call ethyl and there is a space between the root and this group. 2-methylbutyl 3-methylbutanoate Notice that the 1 position is attached to oxygen for both the root and the alkyl group on the oxygen. methyl ethanoate ethyl ethanoate methyl butanoate If you need additional review I highly recommend the University of Calgary nomenclature website at The above examples are simple enough that I expect them with a high probability on your exam. Can more complex systems be tested? Hypothetically yes anything on the link above. But remember its worth 1-2 marks and the above should be good enough for your exam. You will see different naming schemas in the future many of which are deprecated. (old names that are no longer in use)