Answer
Organic compounds are principally sourced from carbon-based sources such as petroleum, coal and natural gas (fossil fuels).
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Yes, Carbon Dioxide could be the source of all naturally occurring organic compounds.
Work Step by Step
Organic compounds can also be sourced from plants and animals for the proteins, fats, carbohydrates, vitamins, etc., present within them.
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Fossil fuels are essentially dead plants, and since plants source their carbon from Carbon Dioxide, $CO_{2}$ can be considered to be the source of all naturally occurring major organic compounds.
