Thioesters are similar to esters, except a sulfur is in place of the oxygen. Another way of thinking of an ester is that it is a carbonyl bonded to an alcohol (with loss of the OH hydrogen). In esters, the carbonyl carbon is bonded to an oxygen which is itself bonded to another carbon. Another way of thinking of an amide is that it is a carbonyl bonded to an amine. The nitrogen in an amide can be bonded either to hydrogens, to carbons, or to both. In amides, the carbonyl carbon is bonded to a nitrogen. The eponymous member of this grouping is the carboxylic acid functional group, in which the carbonyl is bonded to a hydroxyl (OH) group.Īs the name implies, carboxylic acids are acidic, meaning that they are readily deprotonated to form the conjugate base form, called a carboxylate (much more about carboxylic acids in Chapter 20). If a carbonyl carbon is bonded on one side to a carbon (or hydrogen) and on the other side to a heteroatom (in organic chemistry, this term generally refers to oxygen, nitrogen, sulfur, or one of the halogens), the functional group is considered to be one of the ‘ carboxylic acid derivatives’, a designation that describes a grouping of several functional groups. We will learn more about the structure and reactions of aromatic groups in Chapter 15. Aromatic groups are planar (flat) ring structures, and are widespread in nature. The aromatic group is exemplified by benzene (which used to be a commonly used solvent on the organic lab, but which was shown to be carcinogenic), and naphthalene, a compound with a distinctive 'mothball' smell. As we will see in Chapter 7, 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. In the example below, the difference between cis and trans alkenes is readily apparent.Īlkanes, alkenes, and alkynes are all classified as hydrocarbons, because they are composed solely of carbon and hydrogen atoms. 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. Functional Groups with Single Bonds to Heteroatoms.Molecules with Multiple Functional Groups.Functional Groups with Carbon Single Bonds to other Atoms.
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