2.5 omeric alkanes the butane Ill pm 153pm Methane 2.1 Structures of trace amounts of unpleasant-smelling sulfur-containing compounds such as ethanethiol (see Table 2. 1) that are deliberately added to it in order to warn us of potentially dan and bond angles gerous leaks. Natural gas is colorless and nearly odorless, as are methane, ethane, and propane Methane is the lowest boiling alkane, followed by ethane, then propane CHA CH3 CH3 CH3CH, CH Propar text are at 1 atm(760 mm of Boiling point:-160°C mercury)unless otherwise This will generally be true as we proceed to look at other alkanes; as the number of car bon atoms increases, so does the boiling point. All the alkanes with four carbons or less are gases at room temperature and atmospheric pressure. with the highest boiling point of the three, propane is the easiest one to liquefy. We are all familiar with"propane tanks. These are steel containers in which a propane-rich mixture of hydrocarbons called liquefied petroleum gas(LPG) is maintained in a liquid state under high pressure convenient clean-burning fuel The structural features of methane, ethane, and propane are summarized in Figure 2.1. All of the carbon atoms are sp-hybridized, all of the bonds are o bonds, and the Modeling software to reproduce bond angles at carbon are close to tetrahedral so that you can better view their 2.5 ISOMERIC ALKANES: THE BUTANES Methane is the only alkane of molecular formula CH4, ethane the only one that is C2H and propane the only one that is C3Hg. Beginning with C4Hio, however, constitutional isomers(Section 1. 8)are possible; two alkanes have this particular molecular formula In one, called n-butane, four carbons are joined in a continuous chain. The n in n-butane stands for"normal and means that the carbon chain is unbranched. The second isomer has a branched carbon chain and is called isobutane CH:,,CH CHaCHCH or(CH3)3CH △ ake molecular models of the two isomers of Cah Boiling point: 0.4°C 10.2°C Melting poin 139°C 160.9°C As noted earlier(Section 1. 16), CH3 is called a methyl group. In addition to having methyl groups at both ends, n-butane contains two CH2, or methylene groups. Isobutane con- tains three methyl groups bonded to a CH unit. The Ch unit is called a methine group Back Forward Main MenuToc Study Guide ToC Student o MHHE Websitetrace amounts of unpleasant-smelling sulfur-containing compounds such as ethanethiol (see Table 2.1) that are deliberately added to it in order to warn us of potentially dan￾gerous leaks. Natural gas is colorless and nearly odorless, as are methane, ethane, and propane. Methane is the lowest boiling alkane, followed by ethane, then propane. This will generally be true as we proceed to look at other alkanes; as the number of car￾bon atoms increases, so does the boiling point. All the alkanes with four carbons or less are gases at room temperature and atmospheric pressure. With the highest boiling point of the three, propane is the easiest one to liquefy. We are all familiar with “propane tanks.” These are steel containers in which a propane-rich mixture of hydrocarbons called liquefied petroleum gas (LPG) is maintained in a liquid state under high pressure as a convenient clean-burning fuel. The structural features of methane, ethane, and propane are summarized in Figure 2.1. All of the carbon atoms are sp3 -hybridized, all of the bonds are bonds, and the bond angles at carbon are close to tetrahedral. 2.5 ISOMERIC ALKANES: THE BUTANES Methane is the only alkane of molecular formula CH4, ethane the only one that is C2H6, and propane the only one that is C3H8. Beginning with C4H10, however, constitutional isomers (Section 1.8) are possible; two alkanes have this particular molecular formula. In one, called n-butane, four carbons are joined in a continuous chain. The n in n-butane stands for “normal” and means that the carbon chain is unbranched. The second isomer has a branched carbon chain and is called isobutane. As noted earlier (Section 1.16), CH3 is called a methyl group. In addition to having methyl groups at both ends, n-butane contains two CH2, or methylene groups. Isobutane con￾tains three methyl groups bonded to a CH unit. The CH unit is called a methine group. CH3CH2CH2CH3 n-Butane 0.4°C 139°C Boiling point: Melting point: CH3CHCH3 W CH3 (CH3) or 3CH Isobutane 10.2°C 160.9°C CH4 Methane Boiling point: 160°C CH3CH3 Ethane 89°C CH3CH2CH3 Propane 42°C 2.5 Isomeric Alkanes: The Butanes 57 109 pm Methane 109.5
153 pm Ethane 111
111 pm 153 pm Propane 111 pm 112
FIGURE 2.1 Structures of methane, ethane, and propane showing bond dis￾tances and bond angles. Boiling points cited in this text are at 1 atm (760 mm of mercury) unless otherwise stated. Use your Learning By Modeling software to reproduce the models shown in Figure 2.1 so that you can better view their three-dimensional shapes. Make molecular models of the two isomers of C4H10. Back Forward Main Menu TOC Study Guide TOC Student OLC MHHE Website