Saturated and unsaturated compounds

 

In organic chemistry, a saturated compound is a chemical compound that has a chain of carbon atoms linked together by single bonds and has hydrogen atoms filling all of the other bonding orbitals of the carbon atoms. Alkanes are an example of saturated compounds. An unsaturated compound is a chemical compound that contains carbon-carbon double bonds or triple bonds, such as those found in alkenes or alkynes, respectively. Saturated and unsaturated compounds need not consist only of a carbon atom chain. They can have functional groups, as well. It is in this sense that fatty acids are classified as saturated or unsaturated. The amount of unsaturation of a fatty acid can be determined by finding its iodine number.

 

In a chain of carbons, such as a fatty acid, a double or triple bond will cause a kink in the chain. These links have macro-structural implications. Unsaturated fats tend to be liquid at room temperature, rather than solid, due to the kinks in the chain. The kinks prevent the molecules from packing closely together to form a solid. These fats are called oils and are present in fish and plants.

 

In other unsaturated hydrocarbons, the double bond between two carbons prevents rotation of the atoms about the bond, locking them into specific structural formations. When attached atoms occupy similar positions on each carbon, they are referred to as "cis", and when they are on opposite sides, they are called "trans". Most natural hydrocarbons exist in the cis state, but artificially manufactured hydrocarbons are trans. The body lacks the enzymes to properly break down the trans configuration. This is why trans fats sare viewed as dangerous and unhealthy, as they tend to build up. Unsaturated compounds of the two formations are classified as geometric isomers of one another.

Organic Molecules and Hydrocarbons

Organic Molecules and Hydrocarbons

Structure of the hydrocarbon methane

You may recall that atoms can be held together by covalent bonds, which are chemical bonds between atoms that share an electron pair. Organic molecules are molecules that contain carbon atoms, which are covalently bonded together. This category of molecules includes gasoline, sugar, proteins and everything in between. Many of these molecules contain other types of atoms as well, but today we're going to focus on molecules that consist of the two most common atoms in organic chemistry: carbon and hydrogen.
Carbon and hydrogen can come together in different ways and can form many, many distinct molecules, which are collectively called hydrocarbons. Hydrocarbons are molecules that are made of hydrogen and carbon atoms.

Saturated Hydrocarbons

 

The simplest organic molecule is methane, CH4, which contains one carbon atom and four hydrogen atoms. This molecule makes up much of what we call 'natural gas' that comes out of gas stoves in our houses. Methane is a saturated hydrocarbon. Saturated hydrocarbons are hydrocarbons that contain no rings and contain only single bonds between the different atoms. Methane is the simplest hydrocarbon because it contains only one carbon atom.

Methane is saturated because it has 2N + 2 hydrogen atoms

What about when it gets a little bit more complicated? How can we figure out whether a hydrocarbon is saturated? You can tell whether or not a hydrocarbon is saturated by using the saturation formula and the molecule's chemical formula. Saturated hydrocarbons have 2N + 2 hydrogen atoms, where N is the number of carbon atoms in the molecule. To put this formula into action, first we count the number of carbon atoms in the molecule (N in the formula). According to the saturation formula, we need 2N + 2 hydrogen atoms to make a saturated hydrocarbon. Methane contains one carbon atom, so for it to be saturated, it needs 2 * 1 (the number of carbon atoms in the molecule) + 2 hydrogen atoms, or 2 + 2 = 4 hydrogen atoms.

 

Alkanes, Alkenes and Alkynes

 

 

A hydrocarbon that contains no double bonds is called an alkane, or hydrocarbon containing only single bonds. Methane and ethane are both alkanes. For each element of unsaturation, which is a ring or double bond in a molecule, the total number of hydrogens in the hydrocarbon will decrease by two. Hydrocarbons that contain rings or double bonds are called unsaturated hydrocarbons, which are the opposite of saturated hydrocarbons. Alkanes - such as cyclohexane, which is an important precursor to nylon - that contain rings of carbon atoms are unsaturated.
Another example of a hydrocarbon is ethylene. Ethylene is an important building block in making plastic and also is involved in the ripening of fruit. Ethylene contains two carbon atoms and is an alkene. An alkene is a hydrocarbon that contains a carbon-carbon double bond. All alkenes by definition are unsaturated because of the double bonds. If we wanted to figure out how many hydrogen atoms ethylene has, we could just use the saturation formula. A saturated two-carbon hydrocarbon would have 2 * 2 (the number of carbons) + 2 hydrogen atoms to make 6 total hydrogen atoms. We know that ethylene has one element of unsaturation, which is the double bond, so we can figure out that ethylene has only four hydrogen atoms and its chemical formula is C2H4.

Alkenes are hydrocarbons that have carbon-carbon double bonds

It's also possible for hydrocarbons to contain carbon-carbon triple bonds; that is, two carbon atoms that share three electron pairs between them. These hydrocarbons that contain carbon-carbon triple bonds are called alkynes. Ethyne, which is also known as acetylene and is used in welding torches, is the simplest alkyne. It has two carbon atoms and contains two hydrogen atoms. As organic molecules get larger, their structures can get much more complex than just a simple chain.

SATURATED HYDROCARBONS AND HALIDE ALKYNE

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon.Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls.}

 Aromatic hydrocarbons (arenes), alkanes, alkenes, cycloalkanes and alkyne-based compounds are different types of hydrocarbons.
The majority of hydrocarbons found on earth naturally occur in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen which, when bonded, can catenate to form seemingly limitless chains.