Different Styles Of Drawing Organic Molecules
In organic chemistry, there are multiple styles used to draw organic molecules. These are: Lewis structures, condensed structures and bond line structures.
In Lewis structures, all of the atoms and bonds are shown. In condensed structures only atoms are shown and not bonds. It is very important to understand and go from a condensed structure to a Lewis structure.
How To Convert Condensed Structure Into Lewis Structure
The main rule is that you must give every neutral carbon four bonds when drawing a Lewis structure from condensed structure. Hydrogen can have one bond only!
Let’s understand the use of parenthesis as well. (CH3)2C means there are two CH3 groups attached to the carbon. (CH3)3C means there are three CH3 groups attached to the carbon. Sometimes parenthesis are used to shorten the writing or show a brach, which you will see during our practice.
CHO = represents aldehyde functional group
COOH = represents carboxylic acid functional group
Finally, numbering carbons in a chain will help you track every carbon and avoid confusion.
Let’s do some practice and convert condensed structures on the left to Lewis dot structures.
Let’s begin with a simple example. We number the carbons and draw the Lewis structure as you read the condensed structure from left to right, making sure that every carbon has 4 bonds.
Again, number the carbons and draw out the Lewis structure. Every carbon has four bonds. Oxygen is between the second and third carbons. Oxygen wants to have two bonds to be neutral.
Number the carbons and draw out the Lewis Structure. CHO represents an aldehyde group. If you didn’t know this, but made sure that every carbon has four bonds, you would still get the correct answer. If you drew the third carbon with one bond to oxygen, you would realize it does not have four bonds and would have to double bond it to the oxygen. Again, oxygen wants to have two bonds to be neutral.
Here we see COOH. COOH is a carboxylic acid functional group as shown in the Lewis dot structure.
(CH3)2CH means there are two CH3 groups attached to the carbon.
Parenthesis inside the condensed formula are often used to write the formula shorter. In this example (CH2)2 is written instead of CH2CH2.
LINKS
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References:
Organic Chemistry by David Klein
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