Ch 11 Intro to Organic Chemistry: Hydrocarbons

Reactions of Benzene

-Benzene undergoes two typical classes of reactions -ALKYLATION (addition of alkyl groups) -HALOGENATION (substituent of Cl or Br) -You will only be responsible for halogenation reactions. -Halogenation of benzene is different from that of alkenes -Only one halogen atom is added, and the benzene ring loses a hydrogen atom. -The reaction is very slow unless a catalyst is added.

Hydrocarbons

-HYDROCARBONS: are organic compounds that contain only carbon and hydrogen. -In organic molecules, every carbon has four bonds. -SATURATED HYDROCARBONS: contain only single bonds.

Reactions of Alkenes and Alkynes

-In a HALOGENATION REACTION, an alkene or alkyne reacts with chlorine (Cl2) or bromine (Br2) -In the case of an alkene, one halogen atom adds to each side of the double bond. -For alkynes, the carbon atoms involved in the triple bond each form two bonds with the halogen. -The BROMINE TEST is a way of testing a compound for double or triple bonds. -the red color of bromine disappears quickly when it reacts with alkenes and alkynes, leaving a colorless solution.

Aromatic Nomenclature

-Naming Aromatic Hydrocarbons -MONOSUBSTITUTED BENZENES (Substituent Group) benzene -DISUBSTITUTED BENZENES Numbering System -determined by the alphabetical order of the substituents. -Di and ORTHO META or PARA

Reactions of Alkenes and Alkynes

-Water will also add to an alkene in the presence of an acid catalyst. -We will use H2SO4 as our catalyst. -This reaction also follows Markovnikov's Rule. -H adds to the carbon bonded to the most H atoms, and OH bonds to the carbon bonded to the least number of H atoms.

Reactions of Alkenes and Alkynes (continued 2).

-When an alkene reacts with HCl, HBr, or HI, a HYDROHALOGENATION REACTION occurs. -This reaction follows MARKOVNIKOV'S RULE which tells us that the hydrogen atom will go on the carbon atom which is bonded to the most hydrogen atoms and that the halogen will go on the other atom. -If both sides of the alkene is bonded to the same number of hydrogen atoms then Markovnikov's rule does not apply.

Halogenation Reactions

-When we add a halogen (usually Br2 or Cl2) to an alkane, a halogen atom may SUBSTITUTE for a hydrogen atom. Heat or light is essential for this reaction to work. -We will only consider MONOHALOGENATION in this class, where exactly one hydrogen atom is substituted. -In reality, more than one hydrogen atom may be substituted, giving many different products.

Learning Check: Select the correct name for each compound.

1) B. Chlorobenzene 2) C. 1,3-dimethylbenzene

How to Name a Compound

1. Find the longest chain in the molecule. 2. Number the chain from the end nearest the first substituent encountered. 3. List the substituents as a prefix along with the number(s) of the carbon(s) to which they are attached. If there is more than one type of substituent in the molecule, list them alphabetically.

11.2 Alkanes

A large number of carbon compounds are possible because the covalent bond between carbon atoms, such as those in hexane, C6H14, are very strong.

Learning Check: Identify the following compounds as an alkene or alkyne:

A. Alkene B. Alkyne

Learning Check: Give the IUPAC name for each of the following compounds: A. B.

A. An alkane with eight continuous carbon atoms is OCTANE. B. A cyclic molecule with five carbon atoms is CYCLOPENTANE.

Learning Check: Name the following alkanes: A. CH3--CH2--CH2--CH3 B. C. CH3--CH2--CH2--CH2--CH2--CH2--CH2--CH3 D.

A. BUTANE B. CYCLOPROPANE C. OCTANE D. CYCLOHEXANE

Learning Check: Given the following expanded structural formula, provide the A. molecular formula B. Condensed structural formula C. Compound name

A. C5H12 B. CH3-CH2-CH2-CH2-CH3 C. PENTANE

Learning Check: Write the condensed structural formula for A. ethane B. heptane

A. CH3-----CH3 B. CH3--CH2--CH2--CH2--CH2--CH2--CH3

Naming Alkanes

ALKANES -are hydrocarbons that contain only C-C and C-H bonds -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.

Identifying Alkenes

ALKENES: contain one or more carbon-carbon double bonds. In ethene, C2H4, two carbon atoms are connected by a double bond. Each carbon atom in the double bond is attached to two hydrogen atoms and has a trigonal planar arrangement with bond angles of 120 degrees.

Identifying Alkynes

ALKYNES: contain one or more carbon-carbon triple bonds. In ethyne, C2H2, -two carbon atoms are connected by a triple bond. -each carbon is also bonded to one H atom. Each carbon atom in the triple bond has a linear arrangement with bond angles of 180 degrees.

Hydrogenation of Oils

Adding H2 to double bonds in vegetable oils produces -compounds with higher melting points. -solids at room temperature, such as margarine, soft margarine, and shortening.

Writing Skeletal Formulas

Alkane compounds can also be represented by their -MOLECULAR FORMULAS, which give the total number of carbon and hydrogen atoms. -LINE-ANGLE FORMULAS, which show the carbon skeleton in which carbon atoms are represented at the end of each line or at each corner.

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.

Condensed Structural Formulas (continued)

Alkanes are written with structural formulas that are -EXPANDED to show each bond. -CONDENSED to show each carbon atom and its attached hydrogen atoms.

Uses of Alkanes

Alkanes with one to four carbons are gases at room temperature and are widely used as heating fuels. Alkanes with five to eight carbons are highly volatile liquids at room temperature, making them useful as fuels. Alkanes with 9-17 carbons are liquids with higher boiling points and are found in motor oils, mineral oil, kerosene, diesel, and jet fuels. -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.

Combustion of Alkanes

Alkanes with strong C-----C bonds -react with oxygen gas to make carbon dioxide and water in combustion reactions. -release energy when C-----C bonds are broken in combustion reactions. CH4(g) + 2O2(g) ----------> CO2(g) + H2O(g) + energy Methane is the natural gas used to cook our food on gas cooktops and to heat our homes.

Alkenes and Alkynes

Alkenes and alkynes are families of hydrocarbons that -contain double and triple bonds, respectively -are called unsaturated hydrocarbons because they do not contain the maximum number of hydrogen atoms. -react with hydrogen gas to increase the number of hydrogen atoms and become alkanes.

Organic Compounds

An ORGANIC COMPOUND -is a compound made from carbon and hydrogen atoms. -may also contain other nonmetals such as oxygen, sulfur, nitrogen, phosphorus, or a halogen. -is often found in common products such as gasoline, medicines, shampoos, plastics, and perfumes. -The formulas of organic compounds are written with carbon first, followed by hydrogen, and then any other elements.

Alkane Representations

An alkane molecule can be represented in several ways: -as a molecular formula -as a ball-and-stick model -as an expanded structural formula -as a condensed structural formula -as a line-angle formula

Naming Aromatic Compounds

Aromatic compounds containing a benzene ring and as ingle substituent are named as benzene derivatives. Since the ring contains only one substituent, the ring is not numbered. Some common names such as toluene, aniline, and phenol are allowed by IUPAC rules. When there are two or more substituents, the benzene ring is numbered to give the lowest numbers to the substituents.

11.8 Aromatic Compounds

Benzene is -an AROMATIC COMPOUND -a ring of six C atoms, each bonded to one H atom -a flat ring structure drawn with three alternating double bonds. -represented by two structures because the electrons are shared equally among all the C atoms. -represented by a skeletal formula using a circle in the center instead of the alternating double bonds.

Aromatic Nomenclature (Continued)

Benzene ring as a substituent

Combustion of Butane

Butane -is used in portable burners -undergoes combustion and produces enough energy to cook food. 2C4H10(g) + 13O2(g) ----> 8CO2(g) + 10H2O(g) + energy

Cis-Trans Isomers (Continued)

CIS-TRANS ISOMERS: have different physical and chemical properties. You can make a "double bond" with your fingers with both thumbs on the same side or opposite from each other.

Cycloalkanes

CYCLOALKANES -are cyclic alkanes -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.

Naming Cycloalkenes

CYCLOALKENES: have a double bond within a ring structure and -are named by assigning the double bond to be between carbon 1 and carbon 2 when a substituent is on the ring. -do not need to include the numbers for the double bond. The carbon atoms in the ring are numbered to give the double bond numbers 1 and 2, then the lowest possible number to any substituents present.

Ethene, C2H4

ETHENE, C2H4, more commonly called ethylene, -is an important plant hormone involved in promoting the ripening of fruits such as bananas. -accelerates the breakdown of cellulose in plants, which causes flowers to wilt and leaves to fall from trees.

11.5 Alkenes and Alkynes

Ethyne, commonly called acetylene, is used in welding, where it reacts with oxygen to produce flames with temperatures above 3300 degrees C.

Hydrogenation

In HYDROGENATION, -hydrogen atoms add to the carbon atoms of a double bond or triple bond. -a catalyst such as Pt, Ni, or Pd is used to speed up the reaction.

Cis-Trans Isomers of Butene

In a CIS ISOMER, the alkyl groups are attached on the same side of the double bond and H atoms are on the other side. In a TRANS ISOMER, the alkyl groups and H atoms are attached on opposite sides of the double bond.

Condensed Structural Formulas

In a CONDENSED STRUCTURAL FORMULA, -each carbon atom and its attached hydrogen atoms are written as a group. -a subscript indicates the number of hydrogen atoms bonded to each carbon atom. The condensed structural formula of butane has four carbon atoms.

Addition Reactions

In alkenes and alkynes, the double and triple bonds are -very reactive, adding H-H and H-OH to the carbons in the double or triple bond -easily broken, providing electrons to form new bonds

Cis-Trans Isomers

In an alkene, the double bond -is rigid and does not rotate -holds attached groups in fixed positions -makes cis-trans isomers possible when two different groups are attached to the carbon atoms on each side of the double bond.

Carbon Compounds: Ethane (C2H6)

In ethane, C2H6, each tetrahedral carbon forms three covalent bonds to hydrogen and one to the other carbon. Two-dimensional and three-dimensional representations of ethane, C2H6: (a) space-filling model (b) ball-and-stick model (c) wedge-dash model (d) expanded structural formula (e) condensed structural formula

Hydration Reactions

In hydration reactions, an alkene reacts with water, H-OH, to form an alcohol, and -a hydrogen atom (H---) from water forms a bond with the carbon atom in the double bond with more hydrogen atoms -the ----OH from water forms a bond with the second carbon atom in the double bond with fewer hydrogen atoms. -is catalyzed by a strong acid such as H2SO4.

Carbon Compounds: Methane (CH4)

In methane, CH4, carbon forms four covalent bonds to hydrogen. Methane is tetrahedral and has bond angles of 109 degrees. Two-dimensional and three-dimensional representations of methane, CH4-. (a) space-filling model (b) ball-and-stick model (c) wedge-dash model (d) expanded structural formula (e) condensed structural formula

Organic and 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. Propane, C3H8, is an organic compound used as a fuel. Salt, NaCl, is an inorganic compound composed of Na+ and Cl- ions.

11.1 Organic Compounds

ORGANIC CHEMISTRY: the study of carbon compounds. Organic compounds such as vegetable oil contain carbon and hydrogen.

Properties of Organic Compounds

Organic compounds typically -have covalent bonds -have low melting and boiling points -are flammable and undergo combustion -are not soluble in water. Vegetable oil is a mixture of organic compounds and is not soluble in water.

Learning Check: Name each of the following alkanes: (p. 17)

SOLUTION:

Learning Check: Write an equation for the hydrogenation of 1-butene using a platinum catalyst.

SOLUTION:

Learning Check: 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 has the formula CH3-CH2-CH3. D. It has the formula MgCl2. E. It burns easily in air. F. It has covalent bonds.

SOLUTION: A. INORGANIC B. ORGANIC C. ORGANIC D. INORGANIC E. ORGANIC F. ORGANIC

Learning Check: Draw the condensed structural and line-angle formula for 3-bromo-1-chlorobutane.

SOLUTION: GIVEN: 3-bromo-1-chlorobutane NEED: condensed structural and line-angle formula CONNECT: four carbon chain, one bromo group, and one chloro. 1. Draw the main chain of carbon atoms. -The longest chain has four carbon atoms-BUTANE. C-C-C-C 2. Number the chain and place the substituents on the carbons indicated by the numbers. 3-bromo: ------Br goes on carbon 3 1-chloro------- Cl goes on carbon 1 3. For the condensed structural formula, add the correct number of hydrogen atoms to give four bonds to each C atom.

Learning Check: Give the IUPAC name for the following compound:

SOLUTION: GIVEN: five-carbon chain, one methyl group, one chloro group NEED: IUPAC name Connect: position of substituents on the carbon chain. 1. Write the alkane name for the longest chain of carbon atoms. -The longest chain has five carbons-PENTANE. 2. Number the carbon atoms from the end nearer a substituent. 3. Give the location and name for each substituent (alphabetical order) as a prefix to the name of the main chain.

Learning Check: In the butane molecule, C4H10, predict the shape around each carbon atom.

SOLUTION: Each carbon atom has four single covalent bonds and, therefore, a tetrahedral shape.

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, C4H10, has two structural isomers: a STRAIGHT CHAIN and a BRANCHED CHAIN.

Alkane Substituents

SUBSTITUENTS: are atoms or groups of atoms attached to the carbon chain and include alkyl and halo groups. ALKYL GROUPS are -groups of carbon atoms attached to carbon chains. -named in the IUPAC system with an Yl ending HALO SUBSTITUENTS are -halogen atoms attached to the carbon chain. -named in the IUPAC system as FLUORO, CHLORO, BROMO, or IODO.

Drawing Formulas for Alkanes

The IUPAC name gives all the information needed to draw the condensed structural formula for an alkane.

Naming Alkanes, Alkenes, and Alkynes

The IUPAC names for alkenes and alkynes -are similar to those of alkanes -use the alkane name with the same number of carbon atoms, replacing the ANE ending with ENE. Cyclic alkenes are named as cycloalkenes.

11.6: Cis-Trans Isomers

The atoms or groups of atoms attached to the carbon atoms on the double bond may form two different structures, which are called geometric or cis-trans isomers.

11.7 Addition Reactions

The commercial process of hydrogenation is used to convert the double bonds in vegetable oils to saturated fats to make a more solid product.

11.4 Properties of Alkanes

The different uses of alkane compounds result from their physical properties, including their solubility and density. The solid alkanes that make up waxy coatings on fruits and vegetables help retain moisture, inhibit mold, and enhance appearance.

Naming Cis-Trans Isomers

The prefix of CIS or TRANS is placed in front of the alkene name when the compound is a cis or trans isomer.

Organic Nomenclature

There are three parts to a compound name: -BASE: this tells how many carbons are in the longest continuous chain -SUFFIX: this tells what type of compound it is. -PREFIX: this tells what groups are attached to the chain.

Naming Aromatic Compounds

When a common name such as toluene, phenol, or aniline can be used, -the carbon atom attached to the methyl, hydroxyl, or amine group is numbered as carbon 1. -the other substituents are named alphabetically.

11.3 Alkanes with Substituents

When an alkane has four or more carbon atoms, the atoms can be arranged so that a side group called a branch or SUBSTITUENT is attached to a carbon chain.

Naming Cycloalkanes with Substituents

When one substituent is attached to a carbon atom in a cycloalkane, -the name of the substituent is placed in front of the cycloalkane name. -no number is needed for a single alkyl group or halogen atom. -The IUPAC name for the following cycloalkane is ETHYLCYCLOHEXANE.