Some of the most dangerous volatile organic chemicals pose multiple threats, such as polycyclic aromatic hydrocarbons, or PAHs. These organic chemicals, which feature rings of carbon atoms, are massive problems near combustion sources, such as backyard grills and cigarettes.
Thanks to their known role in causing various forms of cancer, PAHs are heavily regulated worldwide. Understanding VOC concentration trends in the atmospheric environment on one hand, and inside homes and offices on the other hand, is a smart way to start improving people's health.
For instance, VOC emissions from building materials may be more likely in specific weather conditions, and many hazardous construction products can cause exposure problems throughout their entire lifetimes 2. Indoor air quality and VOC go hand-in-hand: High concentrations typically indicate conditions that are prone to accumulate pollutants of all kinds.
Although VOC emission levels aren't the only thing that people should be concerned with, they're good hallmarks of general air quality for those seeking to get healthier. Foobot pioneers innovative air monitoring products, services and technologies that lead to improved air quality indoors. VOCs vs. Organic Chemistry Basics Volatile chemicals are those likely to change into gases.
When more than one substituent is present, either on the same carbon atom or on different carbon atoms, the substituents are listed alphabetically. Because the carbon atom numbering begins at the end closest to a substituent, the longest chain of carbon atoms is numbered in such a way as to produce the lowest number for the substituents. The ending -o replaces -ide at the end of the name of an electronegative substituent in ionic compounds, the negatively charged ion ends with -ide like chloride; in organic compounds, such atoms are treated as substituents and the -o ending is used.
The number of substituents of the same type is indicated by the prefixes di- two , tri- three , tetra- four , and so on for example, difluoro- indicates two fluoride substituents. Naming Halogen-substituted Alkanes Name the molecule whose structure is shown here:.
The four-carbon chain is numbered from the end with the chlorine atom. This puts the substituents on positions 1 and 2 numbering from the other end would put the substituents on positions 3 and 4. Four carbon atoms means that the base name of this compound will be butane. The bromine at position 2 will be described by adding 2-bromo-; this will come at the beginning of the name, since bromo- comes before chloro- alphabetically. The chlorine at position 1 will be described by adding 1-chloro-, resulting in the name of the molecule being 2-bromochlorobutane.
Check Your Learning Name the following molecule:. We call a substituent that contains one less hydrogen than the corresponding alkane an alkyl group. The name of an alkyl group is obtained by dropping the suffix -ane of the alkane name and adding -yl :. The open bonds in the methyl and ethyl groups indicate that these alkyl groups are bonded to another atom. Naming Substituted Alkanes Name the molecule whose structure is shown here:. Solution The longest carbon chain runs horizontally across the page and contains six carbon atoms this makes the base of the name hexane, but we will also need to incorporate the name of the branch.
In this case, we want to number from right to left as shown by the blue numbers so the branch is connected to carbon 3 imagine the numbers from left to right—this would put the branch on carbon 4, violating our rules. The branch attached to position 3 of our chain contains two carbon atoms numbered in red —so we take our name for two carbons eth- and attach -yl at the end to signify we are describing a branch.
Putting all the pieces together, this molecule is 3-ethylhexane. This diversity of possible alkyl groups can be identified in the following way: The four hydrogen atoms in a methane molecule are equivalent; they all have the same environment. They are equivalent because each is bonded to a carbon atom the same carbon atom that is bonded to three hydrogen atoms. It may be easier to see the equivalency in the ball and stick models in Figure 1.
Removal of any one of the four hydrogen atoms from methane forms a methyl group. Likewise, the six hydrogen atoms in ethane are equivalent Figure 1 and removing any one of these hydrogen atoms produces an ethyl group. Each of the six hydrogen atoms is bonded to a carbon atom that is bonded to two other hydrogen atoms and a carbon atom.
However, in both propane and 2—methylpropane, there are hydrogen atoms in two different environments, distinguished by the adjacent atoms or groups of atoms:. Each of the six equivalent hydrogen atoms of the first type in propane and each of the nine equivalent hydrogen atoms of that type in 2-methylpropane all shown in black are bonded to a carbon atom that is bonded to only one other carbon atom.
The two purple hydrogen atoms in propane are of a second type. They differ from the six hydrogen atoms of the first type in that they are bonded to a carbon atom bonded to two other carbon atoms. The green hydrogen atom in 2-methylpropane differs from the other nine hydrogen atoms in that molecule and from the purple hydrogen atoms in propane. The green hydrogen atom in 2-methylpropane is bonded to a carbon atom bonded to three other carbon atoms.
Two different alkyl groups can be formed from each of these molecules, depending on which hydrogen atom is removed. The names and structures of these and several other alkyl groups are listed in Figure 4. Note that alkyl groups do not exist as stable independent entities. They are always a part of some larger molecule. The location of an alkyl group on a hydrocarbon chain is indicated in the same way as any other substituent:. Alkanes are relatively stable molecules, but heat or light will activate reactions that involve the breaking of C—H or C—C single bonds.
Combustion is one such reaction:. Alkanes burn in the presence of oxygen, a highly exothermic oxidation-reduction reaction that produces carbon dioxide and water. As a consequence, alkanes are excellent fuels. For example, methane, CH 4 , is the principal component of natural gas. Butane, C 4 H 10 , used in camping stoves and lighters is an alkane.
Gasoline is a liquid mixture of continuous- and branched-chain alkanes, each containing from five to nine carbon atoms, plus various additives to improve its performance as a fuel. Kerosene, diesel oil, and fuel oil are primarily mixtures of alkanes with higher molecular masses. The main source of these liquid alkane fuels is crude oil, a complex mixture that is separated by fractional distillation.
Fractional distillation takes advantage of differences in the boiling points of the components of the mixture see Figure 5. You may recall that boiling point is a function of intermolecular interactions, which was discussed in the chapter on solutions and colloids. No carbon-carbon bonds are broken in these reactions, and the hybridization of the carbon atoms does not change.
For example, the reaction between ethane and molecular chlorine depicted here is a substitution reaction:. The C—Cl portion of the chloroethane molecule is an example of a functional group , the part or moiety of a molecule that imparts a specific chemical reactivity. The types of functional groups present in an organic molecule are major determinants of its chemical properties and are used as a means of classifying organic compounds as detailed in the remaining sections of this chapter.
Want more practice naming alkanes? Watch this brief video tutorial to review the nomenclature process. Organic compounds that contain one or more double or triple bonds between carbon atoms are described as unsaturated. You have likely heard of unsaturated fats. These are complex organic molecules with long chains of carbon atoms, which contain at least one double bond between carbon atoms.
Unsaturated hydrocarbon molecules that contain one or more double bonds are called alkenes. Double and triple bonds give rise to a different geometry around the carbon atom that participates in them, leading to important differences in molecular shape and properties. The differing geometries are responsible for the different properties of unsaturated versus saturated fats.
Ethene, C 2 H 4 , is the simplest alkene. Each carbon atom in ethene, commonly called ethylene, has a trigonal planar structure. The second member of the series is propene propylene Figure 6 ; the butene isomers follow in the series. Four carbon atoms in the chain of butene allows for the formation of isomers based on the position of the double bond, as well as a new form of isomerism. Ethylene the common industrial name for ethene is a basic raw material in the production of polyethylene and other important compounds.
Over million tons of ethylene were produced worldwide in for use in the polymer, petrochemical, and plastic industries. Ethylene is produced industrially in a process called cracking, in which the long hydrocarbon chains in a petroleum mixture are broken into smaller molecules. Polymers can be natural starch is a polymer of sugar residues and proteins are polymers of amino acids or synthetic [like polyethylene, polyvinyl chloride PVC , and polystyrene].
The variety of structures of polymers translates into a broad range of properties and uses that make them integral parts of our everyday lives. Adding functional groups to the structure of a polymer can result in significantly different properties see the discussion about Kevlar later in this chapter. An example of a polymerization reaction is shown in Figure 7. The monomer ethylene C 2 H 4 is a gas at room temperature, but when polymerized, using a transition metal catalyst, it is transformed into a solid material made up of long chains of —CH 2 — units called polyethylene.
Polyethylene is a commodity plastic used primarily for packaging bags and films. Polyethylene is a member of one subset of synthetic polymers classified as plastics. Plastics are synthetic organic solids that can be molded; they are typically organic polymers with high molecular masses. Most of the monomers that go into common plastics ethylene, propylene, vinyl chloride, styrene, and ethylene terephthalate are derived from petrochemicals and are not very biodegradable, making them candidate materials for recycling.
Recycling plastics helps minimize the need for using more of the petrochemical supplies and also minimizes the environmental damage caused by throwing away these nonbiodegradable materials. Plastic recycling is the process of recovering waste, scrap, or used plastics, and reprocessing the material into useful products.
For example, polyethylene terephthalate soft drink bottles can be melted down and used for plastic furniture, in carpets, or for other applications. Other plastics, like polyethylene bags and polypropylene cups, plastic food containers , can be recycled or reprocessed to be used again. Many areas of the country have recycling programs that focus on one or more of the commodity plastics that have been assigned a recycling code see Figure 8.
These operations have been in effect since the s and have made the production of some plastics among the most efficient industrial operations today. The name of an alkene is derived from the name of the alkane with the same number of carbon atoms. As a result, the benzene has six hydrogens and the formula for a benzene molecule is C 6 H 6. The benzene ring has resonance, meaning that the electron density is delocalized in the ring so that each bond is more similar to 1.
These compounds possess special properties due to the delocalized electron density in benzene, including additional stabilization. A benzene molecule : The benzene molecules and its derivatives are the basis for aromatic structures. Many organic compounds belong in multiple categories. For example, a chemical structure can be both aromatic and contain an alkyne.
Therefore, naming organic compounds can be quite challenging and complicated. The study of hydrocarbons is particularly important to the fields of chemical and petroleum engineering, as a variety of hydrocarbons can be found in crude oil.
This material can be processed to produce compounds for a number of applications.
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