![]() ![]() 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 there is a very high energy barrier to rotation about a double bond. Furthermore, many alkenes can take two geometric forms: cis or trans (or Z and E which will be explained in detail in Chapter 7). Ethyne, commonly called acetylene, is used as a fuel in welding blow torches.Īlkenes have trigonal planar electron geometry (due to sp 2 hybrid orbitals at the alkene carbons) while alkynes have linear geometry (due to sp hybrid orbitals at the alkyne carbons). (If you want bananas to ripen quickly, put them in a paper bag along with an apple - the apple emits ethene gas, setting off the ripening process in the bananas). Ethene, the simplest alkene example, is a gas that serves as a cellular signal in fruits to stimulate ripening. Octane, C 8H 18, is a component of gasoline.Īlkenes (sometimes called olefins) have carbon-carbon double bonds, and alkynes have carbon-carbon triple bonds. Some examples of alkanes include methane, CH 4, is the natural gas you may burn in your furnace or on a stove. The simplest functional group in organic chemistry (which is often ignored when listing functional groups) is called an alkane, characterized by single bonds between two carbons and between carbon and hydrogen. ![]() Add hydrogen atoms to the end of each of these bonds. (and/or at the place where two or more lines meet) Add bonds so that each carbon atom makes 4 bonds. Much of the remainder of your study of organic chemistry will be taken up with learning about how the different functional groups tend to behave in organic reactions. To draw a 2-dimensional (full display) structural formula given the skeletal formula: Place a carbon atom at the end of each line. For now, we will only worry about drawing and recognizing each functional group, as depicted by Lewis and line structures. Because of their importance in understanding organic chemistry, functional groups have specific names that often carry over in the naming of individual compounds incorporating the groups.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. A particular functional group will almost always display its distinctive chemical behavior when it is present in a compound. Gradually they will become familiar, and eventually you will recognize them automatically.įunctional groups are small groups of atoms that exhibit a characteristic reactivity. We expect that you will need to refer back to tables at the end of Section 3.1 quite frequently at first, as it is not really feasible to learn the names and structures of all the functional groups and compound types at one sitting. The concept of functional groups is a very important one. ![]()
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