Unlike molecular formulas, which only list the numbers of each type of atom found in a molecule, structural formulas show how the atoms are connected together in the molecule.
There are several different conventions for drawing structural formulas, some of which are less explicit than others and require some knowledge of chemistry to infer the correct 3-dimensional structure.
In this Elaboration we will start with the 3-dimensional structure of a molecule and then review the different structural formulas that can be used to communicate this 3-dimensional structures. Below is a figure showing the 3-dimensional structure for a 2-propanol molecule.
Later you will learn how to name organic molecules, such as 2-propanol ; you are probably more familiar with this molecule by its more common name, rubbing alcohol. Figure 1: 3-dimensional model of 2-propanol. This model uses balls to represent each of the atoms; carbons C are gray, the oxygen O is red, and the hydrogens H are white.
The sticks connecting the atoms represent the covalent bonds. This kind of model called a ball and stick model. The most explicit type of structural formula is one that we have already used, the electron dot structural formula ; we used electron dot structures earlier to demonstrate how each atom in a molecule has fulfilled the octet rule See Elaboration - The Octet Rule. Shown below is the electron dot structural formula for 2-propanol :. Figure 2: Electron dot structural formula for 2-propanol.
The dots are used to represent the valence electrons. The pairs of bonding electrons are shown in red, while the non-bonding electrons on the oxygen are shown in blue. This structural formula can be made less cluttered by using lines to represent the the pairs of electrons that are participating in the covalent bonds. This produces the line-bond structural formula in which each line represents a pair of bonding electrons. Shown below is the line-bond structural formula for 2-propanol :.
Figure 3: Line-bond structural formula for 2-propanol. The lines are used to represent the covalent bonds. Because the H 2 O molecules are embedded within the compound, the compound is not necessarily "wet". When hydrates are heated, the water in the compound evaporates and the compound becomes anhydrous. These compounds can be used to attract water such as CoCl 2.
When CoCl 2 is dry, CoCl 2 is a blue color wherease the hexahydrate written below is pink in color. Organic compounds contain a combination carbon and hydrogen or carbon and hydrogen with nitrogen and a few other elements, such as phosphorous, sulfur, silicon, and the halogens.
Most organic compounds are seen in biological origin, as they are found in nature. Hydrocarbons are compounds that consist of only carbon and hydrogen atoms. Hydrocarbons that are bonded together with only single bonds are alkanes. The simplest example is methane shown below. When hydrocarbons have one or more double bonds, they are called alkenes. The simplest alkene is Ethene C 2 H 4 which contains a double bond between the two carbon atoms.
Functional groups are atoms connected to carbon chains or rings of organic molecules. Compounds that are within a functional group tend to have similar properties and characteristics. Two common functional groups are hydroxyl groups and carboxyl groups. Hydroxyl groups end in -OH and are alcohols. Functional groups also help with nomenclature by using prefixes to help name the compounds that have similar chemical properties. Methylbutane, C 5 H Analysis of Molecular and Empirical Formulas.
The Many Ways of Drawing Butane. The Principle of Least Effort. Condensed Formulas: Deciphering the Brackets. Common Mistakes: Pentavalent Carbon. Organic Structures. Representing Organic Molecules. Book section on Condensed and line structrures. Condensed formulas.
Molecular formula, structural formula, 3-dimensions. Condensed structures and Lewis Structures. Representing organic structrures. Different type of structure representations. Condensed formulas and line structures. Line structures. Condensed Formulas. Handout describing Line Structures. How to draw skeletal formulas. Molecular Geometry and Structural Formula Understanding how atoms in a molecules are arranged and how they are bonded together is very important in giving the molecule its identity.
Polymers A polymer is formed when small molecules of identical structure, monomers, combine into a large cluster. Ethylene becomes the polymer polyethylene. Molecular Formula The molecular formula is based on the actual makeup of the compound.
Empirical Formula An empirical formula shows the most basic form of a compound. Structural Formula A structural formula displays the atoms of the molecule in the order they are bonded. Condensed Structural Formula Condensed structural formulas show the order of atoms like a structural formula but are written in a single line to save space and make it more convenient and faster to write out. Line-Angle Formula Because organic compounds can be complex at times, line-angle formulas are used to write carbon and hydrogen atoms more efficiently by replacing the letters with lines.
Formulas of Inorganic Compounds Inorganic compounds are typically not of biological origin. Binary compounds Binary compounds are formed between two elements, either a metal paired with a nonmetal or two nonmetals paired together.
For example:. To convert between empirical and molecular formulas, the empirical formula can be multiplied by a whole number to reach the molecular formula. In this case, the empirical formula would be multiplied by 6 to get to the molecular formula.
Molecular formulas contain no information about the arrangement of atoms. Because of this, one molecular formula can describe a number of different chemical structures. A structural formula is used to indicate not only the number of atoms, but also their arrangement in space. A structural formula is not as compact and easy to communicate, but it provides information that the molecular formula does not about the relative positioning of atoms and the bonding between atoms.
Compounds that share a chemical formula but have different chemical structures are known as isomers, and they can have quite different physical properties. Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:.
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