As we will see in chapter 15, hydrogen can be added to double and triple bonds, in a type of reaction called 'hydrogenation'. The double and triple-bonded carbons in alkenes and alkynes have fewer hydrogen atoms bonded to them - they are thus referred to as unsaturated hydrocarbons. Alkanes are said to be saturated hydrocarbons, because the carbons are bonded to the maximum possible number of hydrogens - in other words, they are saturated with hydrogen atoms. We will have more to say about the subject of cis and trans alkenes in chapter 3, and we will learn much more about the reactivity of alkenes in chapter 14.Īlkanes, alkenes, and alkynes are all classified as hydrocarbons, because they are composed solely of carbon and hydrogen atoms. In the example below, the difference between cis and trans alkenes is readily apparent. The cis and trans forms of a given alkene are different molecules with different physical properties because, as we will learn in chapter 2, there is a very high energy barrier to rotation about a double bond. Furthermore, many alkenes can take two geometric forms: cis or trans. In chapter 2, we will study the nature of the bonding on alkenes and alkynes, and learn that that the bonding in alkenes is trigonal planar in in alkynes is linear. Octane, C 8H 18, is a component of gasoline. Methane, CH 4, is the natural gas you may burn in your furnace. The 'default' in organic chemistry (essentially, the lack of any functional groups) is given the term alkane, characterized by single bonds between carbon and carbon, or between carbon and hydrogen. Much of the remainder of your study of organic chemistry will be taken up with learning about how the different functional groups behave in organic reactions.
For now, we will only worry about drawing and recognizing each functional group, as depicted by Lewis and line structures. The structure of capsaicin, the compound discussed in the beginning of this chapter, incorporates several functional groups, labeled in the figure below and explained throughout this section.Īs we progress in our study of organic chemistry, it will become extremely important to be able to quickly recognize the most common functional groups, because they are the key structural elements that define how organic molecules react. \)įunctional groups are structural units within organic compounds that are defined by specific bonding arrangements between specific atoms.
0 kommentar(er)
