Introduction to Organic Chemistry: Hydrocarbons Chapter 12 12.1 Organic Compounds Identify properties characteristic of organic or inorganic compounds. Chapter 12 12.1 Organic Compounds 12.2 Alkanes 12.3 Alkanes with Substituents 12.4 Properties of Alkanes 12.5 Alkenes and Alkynes 12.6 Cis-Trans Isomers 12.7 Addition Reactions for Alkenes 12.8 Aromatic Compounds Organic Compounds Organic chemistry is the study of carbon compounds. An organic compound contains carbon and hydrogen atoms also contain other nonmetals such as oxygen, nitrogen, phosphorus, or a halogen. compounds are found in: Gasoline, medicines, shampoos, plastics, and perfumes Carbohydrates, fats, and proteins Always May Organic
Functional Groups Organic vs. Inorganic In chemistry, molecules are classified as Organic or Inorganic. Organic compounds are organized by their functional groups (groups of atoms bonded in a specific way). Inorganic compounds are (quite expansively) anything that is not organic. Compounds that contain the same functional groups have similar physical and chemical properties. The identification of functional groups allows us to classify organic compounds according to their structure, to name compounds within each family, and to predict their chemical reactions. Organic and Inorganic compounds have different properties. Organic compounds: Have low melting and boiling points. Are flammable and undergo combustion. Are not soluble in water. Inorganic compounds Many inorganic compounds have high melting and boiling points. Inorganic compounds that are ionic are usually soluble in water, and most do not burn in air. Practice Identify each characteristic as most typical of compounds that are inorganic or organic. A. It has a high melting point. B. It is not soluble in water. C. It contains carbon and hydrogen atoms. D. It has the formula MgCl 2. E. It burns easily in air.
Representations of Carbon Compounds Hydrocarbons are organic compounds that consist of only carbon and hydrogen. In organic molecules, every carbon atom has four bonds. In methane (CH4), the carbon atom forms an octet by sharing its four valence electrons with four hydrogen atoms. Three-dimensional and two-dimensional representations of methane: a) space-filling model, b) ball-and-stick model, c) wedge-dash model, d) expanded structural formula, and e) condensed structural formula Alkanes Alkanes are formed by a continuous chain of carbon atoms. are named using the IUPAC (International Union of Pure and Applied Chemistry) system. have names that end in ane. use Greek prefixes to name carbon chains with five or more carbon atoms. Representations of Carbon Compounds In ethane (C 2 H 6 ), each tetrahedral carbon forms three covalent bonds to hydrogen and one to the other carbon. Study Check In the butane molecule (C 4 H 10 ), predict the shape around each carbon atom. H H H H H C C C C H H H H H
Chapter 12 12.1 Organic Compounds 12.2 Alkanes 12.3 Alkanes with Substituents 12.4 Properties of Alkanes 12.5 Alkenes and Alkynes 12.6 Cis-Trans Isomers 12.7 Addition Reactions for Alkenes 12.8 Aromatic Compounds Alkanes More than 90% of the compounds in the world are organic compounds. The larger number of carbon compounds is possible because the covalent bonds between carbon atoms (C-C) is very strong, allowing carbon atoms to form long, stable chains. 12.2 - Alkanes Write the IUPAC names and draw the condensed or line-angle structural formulas for alkanes and cycloalkanes. Alkanes The alkanes are a type of hydrocarbon in which the carbon atoms are connected only by single bonds. Alkanes are formed by a continuous chain of carbon atoms. The names of alkanes and in ane. Such names are part of the IUPAC system (International Union of Pure and Applied Chemistry) used by chemists to name organic chemistry. Alkanes made of carbon chains are named based on how many carbons make up the chain. One of the most common uses of alkanes is as fuels. Methane, propane, octane, and hexane are all alkanes used as fuels.
IUPAC Names of Alkanes Condensed formula and Line-angle formula Pentane Line-Angle Structural Formulas A simplified structure of organic molecules is called the line-angle structural formula. shows a zigzag line in which carbon atoms are represented as the ends of each line and as corners. Carbon atoms at the end are bonded to three hydrogen atoms. in the middle are bonded to two hydrogen atoms. Condensed formula and Line-angle formula Draw the condensed structural formula and name the molecule:
Guide to Drawing Structural Formulas for Alkanes Step 1: Draw the carbon chain. Step 2: Draw the expanded structural formula by adding the hydrogen atoms using single bonds to each of the carbon atoms. Step 3: Draw the condensed structural formula by combining the H atoms with each C atom. Step 4: Draw the line-angle structural formula as a zigzag line in which the ends and corners represent C atoms. Drawing Expanded, Condensed, and Line- Angle Structural Formulas (2 of 3) Draw the expanded, condensed, and line-angle structural formula for pentane. Step 3: Draw the condensed structural formula by combining the H atoms with each C atom. Drawing Expanded, Condensed, and Line- Angle Structural Formulas (1 of 3) Draw the expanded, condensed, and line-angle structural formula for pentane. Step 1: Draw the carbon chain. A molecule of pentane has five carbon atoms in a continuous chain. Step 2: Draw the expanded structural formula by adding the hydrogen atoms, using single bonds to each of the carbon atoms. Drawing Expanded, Condensed, and Line- Angle Structural Formulas (3 of 3) Draw the expanded, condensed, and line-angle structural formula for pentane. Step 4: Draw the line-angle structural formula as a zigzag line in which the ends and corners represent C atoms.
Conformations of Alkanes Single bonds can spin and rotate. Thus different arrangements, known as conformations, occur during the rotation about a single bond. http://symmetry.otterbein.edu/gallery/index.html Structural Formulas: C 4 H 10 Structural Formulas: C 4 H 10 As butane (C 4 H 10 ) rotates, sometimes the line up in front of each other, and at other times they are opposite each other. Butane can be drawn using a variety of two-dimensional condensed structural formulas: Cycloalkanes Hydrocarbons can also form into circles or rings called: cycloalkanes have two fewer hydrogen atoms than the open chain form. are named by using the prefix cyclo before the name of the alkane chain with the same number of carbon atoms.
Formulas of Cycloalkanes Table 12.4 Formulas of Some Common Cycloalkanes Name BLANK BLANK BLANK Cyclopropane Cyclobutane Cyclopentane Cyclohexane Ball-and-Stick Model BLANK BLANK BLANK Three carbons single-bonded to each other in a triangular pattern, The ball and stick model shows four The ball and stick model shows five The ball and stick model shows six with each carbon single-bonded to 2 hydrogens. carbons single-bonded to each other in a carbons single-bonded to each other in carbons single-bonded to each other in square pattern, with each carbon singlebonded to 2 hydrogens. single-bonded to 2 a pentagonal pattern, with each carbon a hexagonal pattern, with each carbon single-bonded to 2 hydrogens. hydrogens. Condensed Structural Formula BLANK BLANK BLANK The condensed structural formula shows a triangular ring of three C The condensed structural formula shows The condensed structural formula The condensed structural formula H 2 molecules. a square ring of four C H 2 molecules. shows a pentagonal ring of five C H 2 shows a hexagonal ring of six C H 2 molecules. molecules. Line-Angle Structural Formula BLANK BLANK BLANK The line-angle structural formula is a triangle. The line-angle structural formula shows a The line-angle structural formula shows The line-angle structural formula shows square. a hexagon. a pentagon. Study Check Name the following alkanes: A. B. C. D. Study Check Give the IUPAC name for each of the following compounds: A. B. Chapter 12 12.1 Organic Compounds 12.2 Alkanes 12.3 Alkanes with Substituents 12.4 Properties of Alkanes 12.5 Alkenes and Alkynes 12.6 Cis-Trans Isomers 12.7 Addition Reactions for Alkenes 12.8 Aromatic Compounds
12.3 Alkanes and Substituents Write the IUPAC names for alkanes with substituents and draw their condensed and line-angle structural formulas. Study Check Draw three possible structural isomers of pentane (C 5 H 12 ). Structural Isomers Structural isomers have the same molecular formula with a different arrangement of atoms. have the same number of atoms bonded in a different order. Butane (C 4 H 10 ) has two structural isomers: a straight chain and a branched chain. Solution Draw three possible structural isomers of pentane (C 5 H 12 ). Structural Isomers of C 5 H 12 Condensed Structural Isomers of C 5 H 12 Structural Isomers of Structural Isomers C 5 H 12 of C 5 H 12 The first condensed structural formula is a straight chain of single-bonded molecules as follows. C H 3, C H 2, C H 2, C H 2, C H 3. The second condensed structural formula is a branched chain as follows. C H 3, C H single-bonded to C H 3 above, The third condensed structural formula is a central C C H 2, C H 3. single-bonded to four C H 3 molecules above, below, rightward, and leftward. Line-Angle The line-angle structural formula shows a zigzag line made of 4 segments forming 3 angles. The line-angle structural formula shows a zigzag of 3 segments forming 2 angles, with The line-angle structural formula shows 2 rising and falling line a fourth segment rising vertically from the first angle. segments with 2 segments rising diagonally right and left from the angle.
Study Check Is the pair of formulas structural isomers? Or the same molecule? Substituents and Alkyl Groups Table 12.5 Formulas and Names of Some Common Substituents Formula Name Formula, C H 3, single bond. name, methyl. Formula, straight chain, C H 3, C H 2, single bond. name, ethyl. BLANK BLANK Formula Name Formula, straight chain, C H 3, C H 2, C H 2, single bond. name, propyl. Formula, branched chain, C H 3, C H with single bond above, C H 3. name, isopropyl. BLANK BLANK Formula Name Formula, straight chain, C H 3, C H 2, C H 2, C H 2, single bond. name, butyl. Formula, branched chain, C H 3, C H single-bonded to C H 3 above, C H 2, single bond. name, isobutyl. Formula, C H 3, C H with single bond above, C H 2, C H 3. name, secondary butyl. Formula, central C with single bond above and three C H 3 molecules below, rightward, and leftward. name, tertiary butyl. Formula Name Formula, F, single bond. name, fluoro. Formula, F, single bond. name, fluoro. Formula, B r, single bond. name, bromo. Formula, I, single bond. name, iodo. Substituents in Alkanes When CH 3 branches off of a carbon chain, it s called an alkyl group When a halogen atom (Group 17) is attached to a carbon chain, it is named as a halo group with the terms fluoro, -chloro, -bromo, -iodo based on which element it is. Naming Alkanes with Substituents
Naming Alkanes with Substituents Naming Cycloalkanes with Substituents Naming Cycloalkanes with Substituents Naming Haloalkanes Haloalkanes are alakanes with a halogen atom that replaces a hydrogen atom. are named by putting the substituents in alphabetical order. have the halo group numbered according to the carbon where it is attached to the alkane. Examples of Haloalkanes BLANK BLANK BLANK BLANK Formula straight chain, C H 3, C l straight chain, C H 3, C H 2, B r Branched chain, C H 3, C H single-bonded to an F above A central C single-bonded to C l above and three C H 3 molecules below, rightward, and leftward IUPAC Chloromethane Bromoethane 2-Fluoropropane 2-Chloro-2- methylpropane Common Methyl chloride Ethyl bromide Isopropyl fluoride Tert-Butyl chloride
Drawing the molecule from the name Draw the condensed and line-angle structural formulas for 2,3-dimethylbutane. Chapter 12 12.1 Organic Compounds 12.2 Alkanes 12.3 Alkanes with Substituents 12.4 Properties of Alkanes 12.5 Alkenes and Alkynes 12.6 Cis-Trans Isomers 12.7 Addition Reactions for Alkenes 12.8 Aromatic Compounds Drawing the molecule from the name Draw the condensed and line-angle structural formulas for 2-bromo-3-ethyl-4-methylpentane. 12.4 Properties of Alkanes Identify the properties of alkanes and write a balanced chemical equation for combustion.
Properties of Alkanes Many types of alkanes are the components of fuels that power our cars and oil that heats our home. The solid alkanes that make up waxy coatings on fruits and vegetables help retain moisture, inhibit mold, and enhance appearance. The different uses of alkane compounds result from their physical properties, including their solubility and density. Uses of Alkanes (2 of 2) Alkanes with 9 17 carbons are liquids with higher boiling points and are found in motor oils, mineral oil, kerosene, diesel, and jet fuels. Decane has 10 carbons: Alkanes with 18 or more carbon atoms, known as paraffins, are waxy solids at room temperature. Petroleum jelly, or Vaseline, is a semisolid mixture of hydrocarbons with more than 25 carbon atoms. Uses of Alkanes (1 of 2) Alkanes with one to four carbons are gases at room temperature and are widely used as heating fuels. methane, ethane, propane, butane Butane has four carbons: Alkanes with five to eight carbons are highly volatile liquids at room temperature, which makes them useful as fuels. pentane, hexane, heptane, octane Octane has eight carbons: Melting and Boiling Points (1 of 4) Alkanes have the lowest melting and boiling points of organic compounds. contain only the nonpolar bonds of exhibit only weak dispersion forces in the solid and liquid states. Longer-chain alkanes have more dispersion forces.
Melting and Boiling Points (2 of 4) Branched alkanes have lower boiling points than the straight-chain isomers. Melting and Boiling Points (3 of 4) Cycloalkanes have higher boiling points than the straight-chain alkanes with the same number of carbon atoms. have limited rotation of carbon bonds; they maintain their rigid structure and can be stacked closely together, which gives them many points of contact and attractions to each other. Melting and Boiling Points (2 of 4) Branched alkanes have lower boiling points than the straight-chain isomers. tend to be more compact, reducing the points of contact between the molecules. do not have linear shapes and cannot line up close to each other. Melting and Boiling Points (4 of 4) We can compare the boiling points of straight-chain alkanes, branched-chain alkanes, and cycloalkanes. Table 12.6 Comparison of Boiling Points of Alkanes and Cycloalkanes with Five Carbons Formula Name Boiling Point ( C) Straight-Chain Alkane BLANK BLANK Straight chain alkanes. condensed structural formula, C H 3, C H 2, C H 2, C H 2, C H 3 Pentane 36 Branched-Chain Alkanes BLANK BLANK Branched chain alkanes. condensed structural formula, C H 3, C H single-bonded to C H 3, C H 2, C H 3 2-Methylbutane 28 Central C single-bonded to four C H 3 molecules Dimethylpropane 10 Cycloalkane BLANK BLANK line-angle structural formula, a pentagonal ring Cyclopentane 49
Combustion of Alkanes (1 of 3) The carbon carbon single bonds in alkanes are difficult to break, which makes them the least reactive family of organic compounds. However, alkanes burn readily in oxygen to produce carbon dioxide, water, and energy. Alkane g O2 g CO2 g H2O g + energy Solubility and Density of Alkanes Alkanes are nonpolar. insoluble in water. less dense than water. flammable in air. found in crude oil. If there is an oil spill in the ocean, the alkanes in the crude oil do not mix with the water but float on top, forming a thin layer on the surface. Combustion of Alkanes (3 of 3) Methane is the natural gas we use to cook our food and heat our homes. The equation for the combustion of methane (CH 4 ) is written as follows: 2 CH g 2O g CO g 2H O g + energy 4 2 2 2 Propane is the gas used in portable heaters and gas barbecues. The equation for the combustion of propane (C 3 H 8 ) is written as follows: CH g 5O g 3CO g 4H O g + energy 4 2 2 2 Chapter 12 12.1 Organic Compounds 12.2 Alkanes 12.3 Alkanes with Substituents 12.4 Properties of Alkanes 12.5 Alkenes and Alkynes 12.6 Cis-Trans Isomers 12.7 Addition Reactions for Alkenes 12.8 Aromatic Compounds