Nomenclature of Organic Compounds

Session 4: Nomenclature of Organic Compounds.

Total Session Time: 120 minutes

Prerequisites

Learning Tasks

By the end of this session students are expected to be able to:

Resources Needed:

SESSION OVERVIEW

|Step |Time |Activity/ |Content |

| | |Method | |

|1 |05 minutes |Presentation |Introduction, Learning Tasks |

|2 |10 minutes |Buzzing |Definition of Nomenclature of |

| | |Presentation |Organic Compounds |

|3 |85 minutes |Group |Nomenclature of organic compounds |

| | |discussion | |

| | |Presentation | |

|4 |10 minutes |Presentation |Key Points |

| 5 |10 minutes |Presentation |Evaluation |

SESSION CONTENTS

STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)

READ or ASK students to read the learning tasks and clarify.

ASK students if they have any questions before continuing.

STEP 2: Definition of Nomenclature of Organic Compounds (10 Minutes).

|Activity: Buzzing (5 minutes) |

| |

|Ask students to brainstorm on the following question: |

| |

|What is nomenclature of organic compounds? |

| |

|ALLOW few students to respond |

| |

|WRITE their responses on the flip chart/ board |

| |

|CLARIFY and SUMMARISE by using the content below |

naming organic chemical compounds as recommended by the International

Union of Pure and Applied Chemistry (IUPAC).

STEP 3: Nomenclature of organic compounds (85 minutes).

|Activity: Small Group Discussion (20 minutes). |

| |

|DIVIDE students into small manageable groups. |

| |

|ASK students to discuss on the following question |

|What are the rules for naming organic compounds? |

| |

|ALLOW students to discuss for 15 minutes. |

| |

|ALLOW few groups to present and the rest to add points not mentioned. |

| |

|CLARIFY and SUMMARIZE by using the contents below. |

The following are the rules that are followed in naming organic

compounds

1. Identification of the parent chain. This chain must obey the following

rules, in order of precedence:

functional group. By suffix, it is meant that the parent functional

group should have a suffix, unlike halogen substituents. If more

than one functional group is present, the one with highest

precedence should be used.

2. Identification of the parent functional group, if any, with the

highest order of precedence.

3. Identification of the side-chains. Side chains are the carbon chains

that are not in the parent chain but are branched off from it.

4. Identification of the remaining functional groups, if any, and naming

oxyalkane for O-R, etc.).

Different side-chains and functional groups will be grouped together

in alphabetical order. (The prefixes di-, tri-, etc. are not taken

into consideration for grouping alphabetically. For example, ethyl

comes before dihydroxy or dimethyl, as the "e" in "ethyl" precedes the

"h" in "dihydroxy" and the "m" in "dimethyl" alphabetically. The "di"

is not considered in either case). When both side chains and secondary

functional groups are present, they should be written mixed together

in one group rather than in two separate groups.

5. Identification of double/triple bonds.

6. Numbering of the chain. This is done by first numbering the chain in

both directions (left to right and right to left), and then choosing

the numbering which follows these rules, in order of precedence

functional group. Locants are the numbers on the carbons to which

the substituent is directly attached.

multiple bond is the number of the adjacent carbon with a lower

number).

7. Numbering of the various substituents and bonds with their locants. If

there is more than one of the same type of substituent/double bond, a

prefix is added showing how many there are ( di – 2 tri – 3 tetra – 4

then as for the number of carbons below with 'a' added)

order and written before the name of the side-chain. If there are two

side-chains with the same alpha carbon, the number will be written

twice. Example: 2,2,3-trimethyl- . If there are both double bonds and

triple bonds, "en" (double bond) is written before "yne" (triple

bond).

which can exist only at the end of a chain, like formyl and carboxyl

groups), there is no need to number it.

1. Arrangement in this form: Group of side chains and secondary

functional groups with numbers made in step 3 + prefix of parent

hydrocarbon chain (eth, meth) + double/triple bonds with numbers (or

"ane") + primary functional group suffix with numbers.

Wherever it says "with numbers", it is understood that between the

word and the numbers, the prefix(di-, tri-) is used.

2. Adding of punctuation:

trimethylheptane becomes 2,5,5-trimethylheptane)

becomes trimethylheptane)

Note: IUPAC uses one-word names throughout. This is why all

parts are connected.

Example

Here is a sample molecule with the parent carbons numbered:

[pic]

For simplicity, here is an image of the same molecule, where the hydrogens

in the parent chain are removed and the carbons are shown by their numbers:

[pic]

Now, following the above steps:

1. The parent hydrocarbon chain has 23 carbons. It is called tricosa-.

2. The functional groups with the highest precedence are the two ketone

groups.

write 3,9-dione.

When numbering from left to right, the ketone groups are

numbered 3 and 9. When numbering from right to left, the ketone

groups are numbered 15 and 21. 3 is less than 15, therefore the

ketones are numbered 3 and 9. The smaller number is always used,

not the sum of the constituent’s numbers.

3. The side chains are: an ethyl- at carbon 4, an ethyl- at carbon 8, and

a butyl- at carbon 12.

Note:The -O-CH3 at carbon atom 15 is not a side chain, but it is a

methoxy functional group.

diethyl.

(But this is not necessarily the final grouping, as functional

groups may be added in between to ensure all groups are listed

alphabetically.)

1. The secondary functional groups are: a hydroxy- at carbon 5, a chloro-

at carbon 11, a methoxy- at carbon 15, and a bromo- at carbon 18.

Grouped with the side chains, this gives 18-bromo-12-butyl-11-chloro-

4,8-diethyl-5-hydroxy-15-methoxy

2. There are two double bonds: one between carbons 6 and 7, and one

between carbons 13 and 14. They would be called "6,13-diene", but the

presence of alkynes switches it to 6,13-dien. There is one triple bond

between carbon atoms 19 and 20. It will be called 19-yne.

3. The arrangement (with punctuation) is: 18-bromo-12-butyl-11-chloro-4,8-

diethyl-5-hydroxy-15-methoxytricosa-6,13-dien-19-yne-3,9-dione

4. Finally, due to Cis-trans isomerism, we have to specify the relative

orientation of functional groups around each double bond. For this

example, we have (6E,13E)

The final name is (6E,13E)-18-bromo-12-butyl-11-chloro-4,8-diethyl-5-

hydroxy-15-methoxytricosa-6,13-dien-19-yne-3,9-dione.

STEP 3: Key Points (5minutes)

which is a systematic method of naming organic chemical compounds as

recommended by the International Union of Pure and Applied Chemistry

(IUPAC).

STEP 4: Evaluation (5 minutes)

References

States: W.B. Saunders Co.

Morrison R.T and Boyd R N (1997). Organic Chemistry (6th Ed.). New Delhi,

India: Prentice Hall of India

Graham Solomon et al (2014). Organic Chemistry (11th Ed.). New Jeysey,

United States: John Willey and Sons.

Rama R. N. (2005). Principles of Pharmaceutical Organic Chemistry. New

Delhi, India: MacMillan Publishers

Bruice Y (2013). Organic Chemistry (7th ed.). New York, United States:

Prentice Hall Pearson.

Delgado J. N. Et al (1998). Wilson and Gisvold's Textbook of Organic

Medicinal and Pharmaceutical Chemistry (10th Ed.). Calfornia, United

States: Lippincott Williams

Bhassin S.K, Gupta R.(2013). Pharmaceutical organic chemistry (E-book

Kindle edition). New Delhi, India: Elsevier Publishing Services

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