9/11/2023 0 Comments Tardigrade carbon backboneWe find ring structures in aliphatic hydrocarbons, sometimes with the presence of double bonds, which we can see by comparing cyclohexane's structure (aliphatic) to benzene (aromatic) in Figure 2.23. Another type of hydrocarbon, aromatic hydrocarbons, consists of closed rings of carbon atoms with alternating single and double bonds. So far, the hydrocarbons we have discussed have been aliphatic hydrocarbons, which consist of linear chains of carbon atoms, and sometimes they can form rings with all single bonds, as shown in Figure 2.23 in the examples of cyclopentane and cyclohexane. Double bonds, like those in ethene, cannot rotate, so the atoms on either side are locked in place. Single bonds, like those in ethane, are able to rotate. When two carbon atoms form a double bond, the shape is planar, or flat. These geometries have a significant impact on the shape a particular molecule can assume.įigure 2.22 When carbon forms single bonds with other atoms, the shape is tetrahedral. 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 2.22 illustrates. ![]() Successive bonds between carbon atoms form hydrocarbon chains. This three-dimensional shape or conformation of the large molecules of life (macromolecules) is critical to how they function. Furthermore, individual carbon-to-carbon bonds may be single, double, or triple covalent bonds, and each type of bond affects the molecule's geometry in a specific way. For this reason, we describe methane as having tetrahedral geometry.įigure 2.21 Methane has a tetrahedral geometry, with each of the four hydrogen atoms spaced 109.5° apart.Īs the backbone of the large molecules of living things, hydrocarbons may exist as linear carbon chains, carbon rings, or combinations of both. The carbons and the four hydrogen atoms form a tetrahedron, with four triangular faces. The shape of its electron orbitals determines the shape of the methane molecule's geometry, where the atoms reside in three dimensions. Methane, an excellent fuel, is the simplest hydrocarbon molecule, with a central carbon atom bonded to four different hydrogen atoms, as Figure 2.21 illustrates. The many covalent bonds between the atoms in hydrocarbons store a great amount of energy, which releases when these molecules burn (oxidize). We often use hydrocarbons in our daily lives as fuels-like the propane in a gas grill or the butane in a lighter. Hydrocarbons are organic molecules consisting entirely of carbon and hydrogen, such as methane (CH 4) described above. 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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