![]() ![]() Geometric isomers, alternatively have similar placements of their covalent bonds but differ in how these bonds are made to the surrounding atoms, especially in carbon-to-carbon double bonds. For example, butane is suited for use as a fuel for cigarette lighters and torches whereas, isobutene is suited for use as a refrigerant and a propellant in spray cans. Structural isomers (like butane and isobutene in (Figure) a) differ in the placement of their covalent bonds: both molecules have four carbons and ten hydrogens (C 4H 10), but the different atom arrangement within the molecules leads to differences in their chemical properties. We call molecules that share the same chemical formula but differ in the placement (structure) of their atoms and/or chemical bonds isomers. The three-dimensional placement of atoms and chemical bonds within organic molecules is central to understanding their chemistry. These geometries have a significant impact on the shape a particular molecule can assume. Double and triple bonds change the molecule’s geometry: single bonds allow rotation along the bond’s axis whereas, double bonds lead to a planar configuration and triple bonds to a linear one. Thus, propane, propene, and propyne follow the same pattern with three carbon molecules, butane, butene, and butyne for four carbon molecules, and so on. The suffixes “-ane,” “-ene,” and “-yne” refer to the presence of single, double, or triple carbon-carbon bonds, respectively. The names of all three molecules start with the prefix “eth-,” which is the prefix for two carbon hydrocarbons. The hydrocarbons ethane, ethene, and ethyne serve as examples of how different carbon-to-carbon bonds affect the molecule’s geometry. Furthermore, a molecule’s different geometries of single, double, and triple covalent bonds alter the overall molecule’s geometry as (Figure) illustrates. Successive bonds between carbon atoms form hydrocarbon chains. This results in a filled outermost shell. Each of its four hydrogen atoms forms a single covalent bond with the carbon atom by sharing a pair of electrons. The methane molecule provides an example: it has the chemical formula CH 4. Therefore, carbon atoms can form up to four covalent bonds with other atoms to satisfy the octet rule. With an atomic number of 6 (six electrons and six protons), the first two electrons fill the inner shell, leaving four in the second shell. Individual carbon atoms have an incomplete outermost electron shell. ![]() ![]() The carbon atom has unique properties that allow it to form covalent bonds to as many as four different atoms, making this versatile element ideal to serve as the basic structural component, or “backbone,” of the macromolecules. The fundamental component for all of these macromolecules is carbon. The macromolecules are a subset of organic molecules (any carbon-containing liquid, solid, or gas) that are especially important for life. Many complex molecules called macromolecules, such as proteins, nucleic acids (RNA and DNA), carbohydrates, and lipids comprise cells. Describe the role of functional groups in biological molecules.Explain why carbon is important for life.By the end of this section, you will be able to do the following: ![]()
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