April 12th - An Intro to Organic Chemistry

Today, we started organic chemistry.

Organic chemistry is the study of carbon compounds. As we know, carbon can form four covalent bonds. This property allows it to form long chains, rings or branches with other carbon compounds. The variety and number of compounds carbon can form is astounding! It’s interesting to note that there are 17 000 000+ organic compounds, but less than 100 000 inorganic compounds.

The simplest organic compounds are made up of carbon and hydrogen.

CH4

CH₃CH₃

As you can see above, there are two ways to write the formula for a compound: condensed and structural. For example, CH₃CH₃ would be the condensed formula, while the image shows the structural formula.

We also learned that saturated compounds have no double or triple bonds. The compounds with only single bonds, which we are currently studying, are called alkanes and always end in ‘-ane’.

Another note: isomers are different compounds with the same empirical formula (like C₅H₂).

There are 3 types of organic compounds:

1. Straight Chains
2. Cyclic Chains
3. Aromatics

We focused solely on straight chains today.

To name them, first circle the longest continuous chain and name this as the base chain.

For example, in the following compound, there is a 7 carbon chain. The longest chain can be identified as the longest path that can be made without going over the same carbon twice. Since there are 7 carbons, we can use the prefix ‘hept-‘ to identify the chain. Here are the guidelines for naming the chains:

• 1 carbon – meth
• 2 carbons – eth
• 3 carbons – prop
• 4 carbons – but
• 5 carbons – pent
• 6 carbons – hex
• 7 carbons – hept
• 8 carbons – oct
• 9 carbons – non
• 10 carbons – dec

We also know that there are only single bonds, so the suffix is ‘-ane’. Therefore, the compound’s primary name is ‘heptane’.

We must also name the side chains. We must number the side chains so that they have the lowest possible aggregate number. Here, we would start counting from the left. The side chains are only one carbon long, so they take the prefix ‘meth-’ and the suffix ‘-yl-. There are three of these, so we give it another prefix: ‘tri-’.

Following all of these rules, the compound is 3, 3, 5 trimethyl heptane.

With that out of the way, now we can do some examples.

Ex.) Name:

This one is pretty easy. The parent chain is 5 carbons long, so it is pentane. Then, numbering properly, we get 2, 2 dimethyl for the side chains. Therefore, the compound is 2, 2 dimethyl pentane. 

Ex.) Draw: 2, 2 dimethyl hexane.

This one is also very easy. First, draw the parent chain. Then, simply add a methyl at the second carbon in the chain:

That's it! As always, he is the video:

Posted by Michael.