Which pair of formulas represents isomers? Table 1.6.a Some Halogenated Hydrocarbons Derived from CH4, Table 1.6.b Some Halogenated Hydrocarbons Derived from CH3CH3. Benzene (C6H6) is of great commercial importance, but it also has noteworthy health effects (see “To Your Health: Benzene and Us”). Which formula represents an alkyl halide? The simplest of these cyclic hydrocarbons has the formula C3H6. Learn how alkane molecules can have branched chains and recognize compounds that are isomers. Even in small amounts, its vapor can cause serious illness if exposure is prolonged. Classify each compound as a cis isomer, a trans isomer, or neither. 0000031307 00000 n For example, methane (CH4) can react with chlorine (Cl2), replacing one, two, three, or all four hydrogen atoms with Cl atoms. Write the structural formula for each compound. We can write the structure of butane (C4H10) by stringing four carbon atoms in a row. (For more information about lipids, see Chapter 7 "Lipids".). This presents a much more serious fire hazard than a natural-gas leak because it is more difficult to rid the room of the heavier gas. Indicate what you would observe. Unfortunately, structural formulas are difficult to type/write and take up a lot of space. Give the correct name for each compound. The physical properties of alkenes are quite similar to those of alkanes. 0000035221 00000 n 0000036694 00000 n It is converted to plastics, isopropyl alcohol, and a variety of other products. Ripening fruits and vegetables give off ethylene, which triggers further ripening. Give the structural formula for the compound represented by this line-angle formula: As noted in Table 1.2 "The First 10 Straight-Chain Alkanes", the number of isomers increases rapidly as the number of carbon atoms increases. Aromatic compounds contain a benzene ring or have certain benzene-like properties; for our purposes, you can recognize aromatic compounds by the presence of one or more benzene rings in their structure. Explain why each compound is less destructive to the ozone layer than are CFCs. 0000036465 00000 n Naphthalene has a pungent odor and is used in mothballs. For example, an alkane with eight carbon atoms has the molecular formula C8H(2 × 8) + 2 = C8H18. Classify each compound as saturated or unsaturated. Which type of name uses numbers to locate substituents—common names or IUPAC names? Plants can synthesize the benzene ring from carbon dioxide, water, and inorganic materials. c. An ethyl substituent is not possible on the second carbon atom; 3,5-dimethylheptane. Many important drugs, a few of which are shown in Table 1.10 "Some Drugs That Contain a Benzene Ring", also feature a benzene ring. The compound at the far right, discovered after the other two, was named neopentane (from the Greek neos, meaning “new”). The molecule seems to be unsaturated, but it does not undergo the typical reactions expected of alkenes. For which member of each pair is hexane a good solvent? Make sure that your printout includes all content from the page. The three simplest alkanes—methane (CH4), ethane (C2H6), and propane (C3H8)—are shown in Figure 1.1 "The Three Simplest Alkanes". Vitamin A, essential to good vision, is derived from a carotene. Write the condensed structural formulas for the four isomers that have the molecular formula C4H9Br. Briefly describe the physical properties of alkenes. A polycyclic aromatic hydrocarbon (PAH) has fused benzene rings sharing a common side. Thus the name for the cyclic compound C4H8 is cyclobutane. These compounds have both polar and nonpolar groups, enabling them to bridge the gap between water-soluble and water-insoluble phases. Some common addition polymers are listed in Table 1.8 "Some Addition Polymers". The CFCs and other Cl- or bromine (Br)-containing ozone-destroying compounds are being replaced with more benign substances. Some cyclic compounds have substituent groups attached. To explain the surprising properties of benzene, chemists suppose the molecule has a cyclic, hexagonal, planar structure of six carbon atoms with one hydrogen atom bonded to each. Cis-trans isomers are compounds that have different configurations (groups permanently in different places in space) because of the presence of a rigid structure in their molecule. Its structure is H–C≡C–H. Draw the structures of the cis-trans isomers for each compound. 0 Cycloalkanes are hydrocarbons whose molecules are closed rings rather than straight or branched chains. Classify each compound as saturated or unsaturated. 0000002968 00000 n Cycloalkyl groups can be derived from cycloalkanes in the same way that alkyl groups are derived from alkanes. A bromo (Br) group is attached to the second carbon atom of the chain. Some representative aromatic compounds and their uses are listed in Table 1.9 "Some Representative Aromatic Compounds", where the benzene ring is represented as C6H5. Draw the structure of benzene as if it had alternate single and double bonds. How are butane and isobutane related? (For more information about polymers and plastics, see Section 1.15 "Polymers".) 0000002475 00000 n b. Any family of compounds in which adjacent members differ from each other by a definite factor (here a CH2 group) is called a homologous series. It exists as both cis and trans isomers: This compound meets rule 2; it has two nonidentical groups on each carbon atom and exists as both cis and trans isomers: 1. The names of other alkynes are illustrated in the following exercises. If the same group appears more than once on the same carbon atom, the number of that carbon atom is repeated as many times as the group appears. Briefly identify the important characteristics of an aromatic compound. It was removed from many product formulations in the 1950s, but others continued to use benzene in products until the 1970s when it was associated with leukemia deaths. Organic fertilizer, such as cow manure, is organic in the original sense; it is derived from living organisms. Adding the groups at their proper positions gives. The vital force theory began to decline in 1828, when the German chemist Friedrich Wöhler synthesized urea from inorganic starting materials. Several halogenated products derived from methane and ethane (CH3CH3) are listed in Table 1.6 "Some Halogenated Hydrocarbons", along with some of their uses. Each of the carbon atoms in the bond can then attach another atom or group while remaining joined to each other by a single bond. For example, large portions of the structures of lipids consist of nonpolar alkyl groups. Methane (CH4), ethane (C2H6), and propane (C3H8) are the beginning of a series of compounds in which any two members in a sequence differ by one carbon atom and two hydrogen atoms—namely, a CH2 unit. An alkyl group is a group of atoms that results when one hydrogen atom is removed from an alkane. (a) propene (b) 1-butanol (c) ethyl propyl ether (d) cis-4-bromo-2-heptene (e) 2,2,3-trimethylhexane (f) formaldehyde. Today, an aromatic compound is any compound that contains a benzene ring or has certain benzene-like properties (but not necessarily a strong aroma). Thus CH3CH2Cl has the common name ethyl chloride and the IUPAC name chloroethane. Atoms or groups attached to this carbon chain, called substituents, are then named, with their positions indicated by numbers. The LCC has six carbon atoms, so the parent compound is hexane (rule 1). Thus the compound CH 2 =CHCH 3 is propene. The reactions of alkanes with halogens produce halogenated hydrocarbons, compounds in which one or more hydrogen atoms of a hydrocarbon have been replaced by halogen atoms: The replacement of only one hydrogen atom gives an alkyl halide (or haloalkane). Natural gas is composed chiefly of methane, which has a density of about 0.67 g/L. Therefore, groups can be either on the same side of the ring (cis) or on opposite sides of the ring (trans). Label them cis and trans. Cyclic structures containing five or six carbon atoms, such as cyclopentane and cyclohexane, are particularly stable. Nevertheless, it is useful to compare typical members of each class, as in Table 1.1 "General Contrasting Properties and Examples of Organic and Inorganic Compounds". What is a substituent? 0000027357 00000 n Alkanes have both common names and systematic names, specified by IUPAC. b. can’t have two groups on one carbon atom on a benzene ring, c. can’t have a substituent on the same carbon atom as the nitro group. How do these properties compare to those of the alkanes? 3. The complete combustion of benzene forms carbon dioxide and water: C6H6 + O2 → CO2 + H2O. Then add the double bond between the second and third carbon atoms: Now place the methyl group on the third carbon atom and add enough hydrogen atoms to give each carbon atom a total of four bonds. Condensed chemical formulas show the hydrogen atoms (or other atoms or groups) right next to the carbon atoms to which they are attached. It’s easier than it looks. These complex molecules (all containing carbon) determine the forms and functions of living systems and are the subject of biochemistry, a topic presented in Chapter 6 "Carbohydrates" through Chapter 11 "Metabolic Pathways and Energy Production". Which reacts least readily? (Hexane, the saturated hydrocarbon with six carbon atoms has the formula C6H14—eight more hydrogen atoms than benzene.) We will not use that prefix here because it is not a part of the system established by the International Union of Pure and Applied Chemistry. Name each cycloalkyl halide. Draw the structure of benzene as chemists usually represent it today. What is an isomer, and how do you find the different ones for one molecule? As we know, alkenes are hydrocarbons with carbon-to-carbon double bonds (R2C=CR2) and alkynes are hydrocarbons with carbon-to-carbon triple bonds (R–C≡C–R). We could name it 2-butene, but there are actually two such compounds; the double bond results in cis-trans isomerism (Figure 1.9 "Ball-and-Spring Models of (a) Cis-2-Butene and (b) Trans-2-Butene"). With more chlorine, a mixture of products is obtained: CH3Cl, CH2Cl2, CHCl3, and CCl4. Give the molecular formulas for methylcyclopentane, 2-methylpentane, and cyclohexane. Collectively, they are called unsaturated hydrocarbons because they have fewer hydrogen atoms than does an alkane with the same number of carbon atoms, as is indicated in the following general formulas: Some representative alkenes—their names, structures, and physical properties—are given in Table 1.7 "Physical Properties of Some Selected Alkenes". If bottled gas escapes into a building, it collects near the floor. Draw its structure and give its name. Briefly identify the important distinctions between a straight-chain alkane and a branched-chain alkane. More reactive than alkanes, alkenes undergo addition reactions across the double bond: Alkenes also undergo addition polymerization, molecules joining together to form long-chain molecules. 0000002332 00000 n For example, alkynes undergo many of the typical addition reactions of alkenes. The compound with this branched chain is called isobutane (Figure 1.4 "Butane and Isobutane"). Here are some basic rules for naming alkenes from the International Union of Pure and Applied Chemistry (IUPAC): The longest chain of carbon atoms containing the double bond is considered the parent chain. 0000005650 00000 n Filling in all the hydrogen atoms gives the following condensed structural formulas: Note that the bonds (dashes) can be shown or not; sometimes they are needed for spacing. If C12H24 reacts with HBr in an addition reaction, what is the molecular formula of the product? We begin our study of organic chemistry with the alkanes, compounds containing only two elements, carbon and hydrogen, and having only single bonds. In ring structures, groups are unable to rotate about any of the ring carbon–carbon bonds. The compound has a benzene ring (with a propyl group substituted for one of the hydrogen atoms); it is aromatic. It ignites readily and burns readily. Which member of each pair has a higher melting point? Name alkynes given formulas and write formulas for alkynes given names. Figure 1.11 Ball-and-Spring Model of Acetylene. It was formerly used to decaffeinate coffee and was a significant component of many consumer products, such as paint strippers, rubber cements, and home dry-cleaning spot removers. They occur mainly over Antarctica from late August through early October and fill in about mid-November. 0000003228 00000 n 0000035819 00000 n Which is a good solvent for cyclohexene, pentane or water? When a natural-gas leak is detected and shut off in a room, the gas can be removed by opening an upper window. Ozone in the upper atmosphere shields Earth’s surface from UV radiation from the sun, which can cause skin cancer in humans and is also harmful to other animals and to some plants. Once widely used in consumer products, many chlorinated hydrocarbons are suspected carcinogens (cancer-causing substances) and also are known to cause severe liver damage. How is the location of a substituent indicated in the IUPAC system? The leak was a mile below the surface, making it difficult to estimate the size of the spill. People crippled by arthritis or injuries gain freedom of movement and relief from pain. Thus, structural formulas identify the specific isomers by showing the order of attachment of the various atoms. Figure 1.12 "Some Benzene Derivatives" shows four examples. Next beyond C4H10 in the homologous series is pentane. It may seem strange that we divide chemistry into two branches—one that considers compounds of only one element and one that covers the 100-plus remaining elements. What is the IUPAC name for the HCFC that has the formula CHCl2CF3? (Some of the names we used earlier, such as isobutane, isopentane, and neopentane, do not follow these rules and are called common names.) Like other hydrocarbons, the alkenes are insoluble in water but soluble in organic solvents. How are they alike? When a common name is used, the carbon atom that bears the group responsible for the name is given the number 1: Name each compound using both the common name and the IUPAC name. and then adding enough hydrogen atoms to give each carbon atom four bonds: The compound butane has this structure, but there is another way to put 4 carbon atoms and 10 hydrogen atoms together. Aromatic hydrocarbons have formulas that can be drawn as cyclic alkenes, making them appear unsaturated, but their structure and properties are generally quite different, so they are not considered to be alkenes. Most of the benzene used commercially comes from petroleum. You can recognize the aromatic compounds in this text by the presence of one or more benzene rings in their structure. For example, butane is called n-butane. Alkane molecules are nonpolar and therefore generally do not react with ionic compounds such as most laboratory acids, bases, oxidizing agents, or reducing agents. The compound is cyclic, but it does not have a benzene ring; it is not aromatic. Alkanes react with oxygen (combustion) and with halogens (halogenation). h�b```f``���d033 �0P������ ��3�(V��a0eX�����E/ς��a�h��[Ò. The condensed formulas show hydrogen atoms right next to the carbon atoms to which they are attached, as illustrated for butane: The ultimate condensed formula is a line-angle formula, in which carbon atoms are implied at the corners and ends of lines, and each carbon atom is understood to be attached to enough hydrogen atoms to give each carbon atom four bonds. Name alkenes given formulas and write formulas for alkenes given names. Hyphens are used to separate numbers from the names of substituents; commas separate numbers from each other. Simplified IUPAC rules for naming alkanes are as follows (demonstrated in Example 12.1). Some common aromatic hydrocarbons consist of fused benzene rings—rings that share a common side. Scientists of the 18th and early 19th centuries studied compounds obtained from plants and animals and labeled them organic because they were isolated from “organized” (living) systems. Table 1.7 Physical Properties of Some Selected Alkenes, We used only condensed structural formulas in Table 1.7 "Physical Properties of Some Selected Alkenes". Draw each structure. The nitro (NO2) group is a common substituent in aromatic compounds. One liter of oil can create a slick 2.5 hectares (6.3 acres) in size. The flat representations shown do not accurately portray bond angles or molecular geometry. (Table 1.2 "The First 10 Straight-Chain Alkanes" has a column identifying the number of possible isomers for the first 10 straight-chain alkanes.) More than half of this ethylene goes into the manufacture of polyethylene, one of the most familiar plastics. Alkanes do not react with many common chemicals. Recognize that alkenes that can exist as cis-trans isomers. Write an equation for the complete combustion of methane (CH4, the main component of natural gas). What is a polymer? The parent chain is butane, indicating four carbon atoms in the LCC. CH3CH2CH2Br, propyl bromide, 1-bromopropane; CH3CHBrCH3, isopropyl bromide, 2-bromopropane, 5. compounds containing Cl, F, and C; by releasing Cl atoms in the stratosphere. Cyclopentane and cyclohexane rings have little strain because the C–C–C angles are near the preferred angles. 0000005160 00000 n Although all three have the same molecular formula, they have different properties, including boiling points: pentane, 36.1°C; isopentane, 27.7°C; and neopentane, 9.5°C. Molecules having carbon-to-carbon double bonds can undergo addition polymerization. We use several kinds of formulas to describe organic compounds. Name cycloalkanes given their formulas and write formulas for these compounds given their names. Larger molecules have greater surface areas and consequently interact more strongly; more energy is therefore required to separate them. What structural feature usually characterizes molecules used as monomers in addition polymerization? Write the equation for the reaction between CH3CH=CHCH3 and each substance. Alkanes react with halogens by substituting one or more halogen atoms for hydrogen atoms to form halogenated hydrocarbons. Lipids include the dietary fats and fatlike compounds called phospholipids and sphingolipids that serve as structural components of living tissues. Moreover, it reacts with water at high temperatures to form deadly phosgene (COCl2) gas, which makes the use of CCl4 in fire extinguishers particularly dangerous. Hydrofluorocarbons (HFCs), such as CH2FCF3, which have no Cl or Br to form radicals, are one alternative. A structural formula shows all the carbon and hydrogen atoms and the bonds attaching them. The general formula for alkynes is CnH2n − 2. Alkenes have physical properties (low boiling points, insoluble in water) quite similar to those of their corresponding alkanes. Name each compound according to the IUPAC system. 0000035885 00000 n 1-Heptene's production and use as an organic synthesis reagent may result in its release to the environment through various waste streams. Methyl groups (rule 2) are attached to the second and fifth carbon atoms. Without referring to a table or other reference, predict which member of each pair has the higher boiling point. A systematic way of naming hydrocarbons and other organic compounds ha s been devised by the International Union of Pure and Applied Chemistry (IUPAC). Give common and IUPAC names for each compound. The IUPAC name for acetylene is ethyne. Draw structures for monomers that can undergo addition polymerization and for four-monomer-unit sections of an addition polymer. All four structures have a double bond and thus meet rule 1 for cis-trans isomerism. 3. We will see in Chapter 6 "Carbohydrates" that some carbohydrates (sugars) form five- or six-membered rings in solution. Aromatic compounds serve as the basis for many drugs, antiseptics, explosives, solvents, and plastics (e.g., polyesters and polystyrene). The most important commercial reactions of alkenes are polymerizations, reactions in which small molecules, referred to in general as monomers (from the Greek monos, meaning “one,” and meros, meaning “parts”), are assembled into giant molecules referred to as polymers (from the Greek poly, meaning “many,” and meros, meaning “parts”). Figure 1.2 The Tetrahedral Methane Molecule. Alkenes have a carbon-to-carbon double bond. Following is the line formula for an alkane. The simplest alkyne—a hydrocarbon with carbon-to-carbon triple bond—has the molecular formula C2H2 and is known by its common name—acetylene (Figure 1.11 "Ball-and-Spring Model of Acetylene"). 0000000016 00000 n For methane (CH4), the reaction is as follows: If the reactants are adequately mixed and there is sufficient oxygen, the only products are carbon dioxide (CO2), water (H2O), and heat—heat for cooking foods, heating homes, and drying clothes. Gas densities are at 1 atm pressure. Write the condensed structural formulas for the two isomers that have the molecular formula C3H7Br. Name the compound and write its condensed structural formula. We begin with the simplest members of a family and then move on to molecules that are organic in the original sense—that is, they are made by and found in living organisms. These are only a few of the many biomedical uses of polymers. Look at the two chlorinated hydrocarbons in Figure 1.8 "Rotation about Bonds". If you could pick up either molecule from the page and flip it over top to bottom, you would see that the two formulas are identical. The substituent names are listed in alphabetical order. 0000023356 00000 n An interesting use of polymers is the replacement of diseased, worn out, or missing parts in the body. Example: Name the following geometric isomers. Explain. An alkyl halide (haloalkane) is a compound resulting from the replacement of a hydrogen atom of an alkane with a halogen atom. The prefixes are fluoro-, chloro-, bromo-, and iodo-. b. octane (a typical hydrocarbon in gasoline). 0000016169 00000 n Table 1.2 The First 10 Straight-Chain Alkanes. (For more information about fats and oils, see Chapter 7 "Lipids", Section 7.1 "Fatty Acids" and Section 7.2 "Fats and Oils".). Name alkanes by the IUPAC system and write formulas for alkanes given IUPAC names. Each succeeding formula incorporates one carbon atom and two hydrogen atoms more than the previous formula. Fluorine (F2), the lightest halogen, combines explosively with most hydrocarbons. One of the doubly bonded carbon atoms does have two different groups attached, but the rules require that both carbon atoms have two different groups. Acetylene (ethyne) is the simplest member of the alkyne family. Alkenes occur widely in nature. Numbers are assigned in the direction that gives the lowest numbers to the carbon atoms with attached substituents. 0000033487 00000 n We will introduce the other three where appropriate. Each carbon atom is understood to be attached to enough hydrogen atoms to give each carbon atom four bonds. Alkenes have double bonds; alkynes have triple bonds. Because displays such as the one above are cumbersome, the polymerization is often abbreviated as follows: Many natural materials—such as proteins, cellulose and starch, and complex silicate minerals—are polymers. (The use of hydrogenation to convert unsaturated vegetable oils to saturated fats is discussed in Chapter 7 "Lipids", Section 7.2 "Fats and Oils".). What is a monomer? Give the name and draw the structure for a compound that illustrates each. Cis-2-butene has both methyl groups on the same side of the molecule. When three isomeric pentenes—X, Y, and Z—are hydrogenated, all three form 2-methylbutane. The carbon atoms in cyclic compounds can be represented by line-angle formulas that result in regular geometric figures. 10. 0000006494 00000 n 0000033373 00000 n Unless otherwise noted, this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. The word organic has different meanings. Consider the line-angle formulas shown here and answer the questions. 203 0 obj <>stream Bromine solutions are brownish red. For example, chlorine reacts with excess methane (CH4) to give methyl chloride (CH3Cl). The artificial ball-and-socket hip joints are made of a special steel (the ball) and plastic (the socket). The substance is insoluble in water and floats on the surface. (Similar reactions with similar results occur with kerosene heaters.). The alkene (CH3)2CHCH2CH=CH2 is named 4-methyl-1-pentene. How do they differ? It is named using the same stem as the alkane having the same number of carbon atoms but ends in -ene to identify it as an alkene. If released to air, a vapor pressure of 59.3 mm Hg at 25 °C indicates 1-heptene will exist solely as a vapor in the ambient atmosphere. To ensure that you understand the material in this unit, you should review the meanings of the bold terms in the following summary and ask yourself how they relate to the topics in the unit. %PDF-1.4 %���� Identify the physical properties of alkanes and describe trends in these properties. Because alkanes have relatively predictable physical properties and undergo relatively few chemical reactions other than combustion, they serve as a basis of comparison for the properties of many other organic compound families. Describe a simple test that distinguishes the two compounds. 0000007017 00000 n The most common aryl group is derived from benzene (C6H6) by removing one hydrogen atom (C6H5) and is called a phenyl group, from pheno, an old name for benzene. We can draw two seemingly different propenes: However, these two structures are not really different from each other. 5. Alkanes are generally unreactive toward laboratory acids, bases, oxidizing agents, and reducing agents. A cyclic hydrocarbon is a hydrocarbon with a ring of carbon atoms. 0000024143 00000 n In alkanes, can there be a two-carbon branch off the second carbon atom of a four-carbon chain? What is addition polymerization? What is the principal difference in properties between alkenes and alkanes? Any hydrocarbon containing either a double or triple bond is an unsaturated hydrocarbon. Crude oil coats the water’s surface in the Gulf of Mexico after the Deepwater Horizon oil rig sank following an explosion. 8. Once widely used as an organic solvent, benzene is now known to have both short- and long-term toxic effects. Nearly all alkanes have densities less than 1.0 g/mL and are therefore less dense than water (the density of H2O is 1.00 g/mL at 20°C). Table 1.5 Physical Properties of Some Alkanes. The LCC has five carbon atoms, and so the parent compound is pentane (rule 1). The lungs become unable to expel fluids, just as in pneumonia caused by bacteria or viruses. trailer This compound meets rule 2; it has two nonidentical groups on each carbon atom (H and Cl on one and H and Br on the other). It can be represented as a square with a CH3 group attached. When sprayed on the skin, it evaporates quickly, cooling the area enough to make it insensitive to pain. The first two alkenes in Table 1.7 "Physical Properties of Some Selected Alkenes"—ethene and propene (Figure 1.7 "Ethene and Propene")—are most often called by their common names—ethylene and propylene, respectively. Those with a larger number of carbon atoms are usually given IUPAC names. The parent chain is heptane in this case, indicating seven carbon atoms in the LCC. (Hint: there are only two. This and similar spills provide a reminder that hydrocarbons and water don’t mix. 0000008481 00000 n The double bond always has priority in numbering. CC BY-NC-SA, Click on the printer icon at the bottom of the screen. The density of air is about 1.29 g/L. Cyclo means a ring compound, hex means 6 carbon atoms, and -ene means a double bond. The compound has a benzene ring (with a chlorine atom substituted for one of the hydrogen atoms); it is aromatic. Note that all the monomers have carbon-to-carbon double bonds. Halogenated cycloalkanes can be named by the IUPAC system. 0000008711 00000 n c. 4-methyl-2-pentene. Indicate whether the structures in each set represent the same compound or isomers. These two compounds are cis-trans isomers (or geometric isomers), compounds that have different configurations (groups permanently in different places in space) because of the presence of a rigid structure in their molecule.
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