Aldehydes and Ketones
Aldehyde and Ketone
1. ALDEHYDE
Definition:
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center (a carbon double bonded to oxygen) bonded to hydrogen and an R group, which is any generic alkyl or side chain. The group without R is called the aldehyde group or formyl group. Aldehydes differ from ketones in that the carbonyl is placed at the end of a carbon skeleton rather than between two carbon atoms. Aldehydes are common in organic chemistry. Many fragrances are aldehydes.
Sources of Aldehydes:
a. Natural and Anthropogenic Aldehydes: Urban, Rural, and Indoor
A trace amount of formaldehyde is present in the air as a result of photochemical oxidation (hydroxyl radicals) of hydrocarbons, for example, methane naturally present in the atmosphere (Atkinson, 1990; Riedel et al., 1999). In rural air, terpenes and isopropene emitted by foliage also react with hydroxyl radicals to form formaldehyde (Atkinson, 1990). In urban areas, motor vehicle exhaust became an important source of aldehydes in air both through direct emission of aldehydes and through the emission of hydrocarbons, which in turn were converted to aldehydes through photochemical oxidation reactions(Cecinato et al., 2002; Destaillats et al., 2002; Grosjean et al., 1996; Maldotti et al., 1980; Rao et al., 2001). The most recent Urban Air Toxics Study results posted on the U.S. Environmental Protection Agency (ERA) web site include formaldehyde, acetaldehyde, and acrolein as significant contributors to the summed risk values for mobile sources of air toxins. These aldehyde air toxins are also regulated under the Canadian Environmental Protection Act (CEPA, 2000a, 2000b). The largest carbonyl emissions were attributed to the oxidation and ring breaking of benzene, toluenes, ethylbenzene, and xylenes in the internal combustion engine or in the exhaust and can be divided into the following four carbonyl
1. ALDEHYDE
Definition:
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center (a carbon double bonded to oxygen) bonded to hydrogen and an R group, which is any generic alkyl or side chain. The group without R is called the aldehyde group or formyl group. Aldehydes differ from ketones in that the carbonyl is placed at the end of a carbon skeleton rather than between two carbon atoms. Aldehydes are common in organic chemistry. Many fragrances are aldehydes.
Sources of Aldehydes:
a. Natural and Anthropogenic Aldehydes: Urban, Rural, and Indoor
A trace amount of formaldehyde is present in the air as a result of photochemical oxidation (hydroxyl radicals) of hydrocarbons, for example, methane naturally present in the atmosphere (Atkinson, 1990; Riedel et al., 1999). In rural air, terpenes and isopropene emitted by foliage also react with hydroxyl radicals to form formaldehyde (Atkinson, 1990). In urban areas, motor vehicle exhaust became an important source of aldehydes in air both through direct emission of aldehydes and through the emission of hydrocarbons, which in turn were converted to aldehydes through photochemical oxidation reactions(Cecinato et al., 2002; Destaillats et al., 2002; Grosjean et al., 1996; Maldotti et al., 1980; Rao et al., 2001). The most recent Urban Air Toxics Study results posted on the U.S. Environmental Protection Agency (ERA) web site include formaldehyde, acetaldehyde, and acrolein as significant contributors to the summed risk values for mobile sources of air toxins. These aldehyde air toxins are also regulated under the Canadian Environmental Protection Act (CEPA, 2000a, 2000b). The largest carbonyl emissions were attributed to the oxidation and ring breaking of benzene, toluenes, ethylbenzene, and xylenes in the internal combustion engine or in the exhaust and can be divided into the following four carbonyl