Butyric acid, for example, has C3H7COOH or CH3CH2CH2CO2H or C4H8O2 (This one also applies to ethyl acetate). Are there different methods for writing formulas?
In: Chemistry
You use a simple formula as required for the situation. Make it so it is simple to read but provide enough information.
C3H7COOH implies that the C3H7 part is a change of carbon 3 carbon with hydrogen attached.
COOH implies a carbon atom with one O that have is doubled bounded and a single bounded O with an H on the other end. COOH is a common way to illustrate a carboxyl group, you can be even clear as (C(=O)OH)
CH3CH2CH2CO2H is the same chain expanded. I am not sure why there is a CO2H insted of COOH at the end..
If you just look at them the shorter that gives you all information if you have some knowledge about the subject is better. The longer is harder to read because you need to count the C in it to get the light.
Compare CH3CH2CO2H CH3CH2CH2CO2H and CH3CH2CH2CH2CO2H versus C2H5COOH C3H7COOH and C4H9COOH
The second is a lot simpler to tell apart to know you have Propionic acid, Butyric acid and Valeric acid
So if you care about chemical properties you need to know the structure
C4H8O2 is appropriate if you for example like to evaluate the mass of the molecule. If you want to know home many moved 10 grams of it is then that information is enough.
You can also look at if to get an idea of the result if you burn. You will get CO2 and H2O so just calculate the number that is needed for the C and H atoms
C4H8O2 + x O2 = 4 CO2+4 H2O
That is 2 O on the right and 12 on the right so you need to add 10 O = 5 O2
Now you know the amount of oxygen used for combustion and you do not need to know the physical strture
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