Naming kinds of Organic Compounds and Rules We Have In Chemistry (NECO GCE CHEMISTRY ANSWERS)

Naming kinds of  Organic Compounds and Rules We Have In Chemistry  (NECO GCE CHEMISTRY ANSWERS)

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Have you ever wondered how compounds like pentane got their name? Discover a practical way to name organic compounds using tried and tested rules. Practice using these rules to name different organic compounds

Video: Naming Organic Compounds: Rules & Practice

Functional Groups in Organic Molecules Next Lesson 

Carbon Is the Key

In organic chemistry there is an atom named carbon. Carbon is one unique atom given the fact that it can form very stable molecules that range in size. Also, carbon can bond with other atoms to create a somewhat endless possibility of organic compounds. How is this possible?

Well, by definition, organic compounds contain a carbon atom. It’s good to keep in mind that almost all organic compounds also contain a hydrogen atom.

How does the carbon atom relate to the process of naming organic compounds? Well, by understanding the meaning of the term, organic compound, we can easily crack the code of naming organic compounds. Let’s take a look.

Naming Organic Compounds

At the most basic level there are three key words to remember when naming organic compounds: prefix, suffix, and the root. Find these, and you are well on your way towards naming an organic compound.

Naming gets complicated, but we can start by applying six steps to all compounds that need to be named. These rules follow a guideline known in organic chemistry as set by the International Union of Pure and Applied Chemistry (IUPAC), which is an authority that creates standards used for naming compounds. Following the IUPAC rules ensures you name every organic structure correctly.

Compound Naming Steps

Step 1: Locate the longest carbon chain in our compound

We will use this compound as our example for naming. As you can see, the longest chain is 7 carbon atoms long.

Step 2: Name that longest carbon chain

Those 7 carbon atoms are equal to a root word. We can find the root word by looking at the table that shows what number of carbon atoms corresponds to what root word. The number 7 corresponds to ‘hept-.’ Now you know that the root word is the base that lets you know how many carbon atoms are in your compound.

Step 3: Figure out what the ending (suffix) should be

If there is a functional group in your compound, you will need to find the suffix that goes with it and put it at the end of your name. A functional group is a specific group of molecules you can easily spot in a compound. For this compound the functional group alkane (C-H atom) is present, so take a look at the table of suffix endings.

You can see that the ending for alkane is ‘-ane.’ When we take our base name of hept- and add -ane, we get that the name for the parent chain (longest carbon-carbon chain) is heptane.

Step 4: Number your carbon atoms

First, notice any side groups, or any molecule or atom that hangs from your longest (or parent) chain. Okay, now locate the two ends of your carbon chain. Begin numbering each carbon atom (1,2, and so on) on the parent chain from left to right, then do it again but from right to left. Which way approaches a side group first? Then that end is considered to be the #1 carbon end.

Hmm, you’ll notice that the carbon attached to our side chain would be numbered 4 no matter which side you come from. Well then, 4 it is! Our side chain will be associated with the number 4, so 4 will come at the very start of our compound’s name.

Step 5: Name the side groups

When you see any endings hanging from the longest carbon chain, circle them. By identifying these you will not forget to include them in the chemical name of your compound. In our compound we have one side chain: a bromine atom that is attached to two carbon atoms. This is a special molecule called bromomethyl.

Step 6: Put the side groups in alphabetical order

After you have circled the side chains, you can include them alphabetically in your final chemical name. Luckily we do not have to alphabetize our side chains as there is only one, called bromomethyl. But keep in mind that when you have multiple side chains, the names must be alphabetized and go before the parent name they are attached to.

Putting all of the steps together what is the name of this compound?

• Side chain location: 4
• Side chain names: bromomethyl
• Root name: hept-
• Functional group name: -ane

That’s right! It is 4-bromomethylheptane. Note that the number 4 refers to the location of the side groups in this compound. When naming, side groups must be assigned the lowest possible number on your parent chain.

Another Example

Let’s take a look at an example. Okay, you’ve counted six carbons on the parent chain, which means the root is ‘hex-‘. Look, a functional group! Alcohol (or OH) is present, so our ending is ‘-ol.’

Now, there’s two side chains, alcohol (OH) and a methyl group (CH3). As we number our carbons, we see that both ends come to a side group at the same time (it takes 3 carbons to get to OH and 3 carbons to get to CH3). When this happens, pick whichever side group is the more complex (has the most atoms) to be the carbon #1 group. CH3 has 4 atoms, and OH only has 2. Therefore CH3 will be the carbon #1 group.

The correct name is 4-methyl-3-hexanol.

Did you notice that the word ‘alcohol’ was not included in our final compound name? If we did then the name would be 4-methyl-3-alcohol-hexanol. This is not correct as alcohol is a functional group. For functional groups we only need two things: (1) the suffix ending ‘-ol’ and (2) its location number.

Lesson Summary

Organic compounds contain carbon atoms. When naming compunds, remember the terms root, suffix, and prefix. Each of these terms are essential when naming an organic compound. The governing standard that creates the rules for naming compound is called IUPAC (International Union of Pure and Applied Chemistry). These rules get complicated, but we’ve tried to simplify them using 6 steps:

1. Locate the longest carbon chain in our compound
2. Name that parent chain (find the root word)
3. Figure out the ending
4. Number your carbon atoms
5. Name the side groups
6. Put the side groups in alphabetical order

Good luck!!