Presentation on theme: "Nivaldo J. Tro Mark Erickson Hartwick College Chapter 6 Organic Chemistry."— Presentation transcript:
Nivaldo J. Tro http://www.cengage.com/chemistry/tro Mark Erickson Hartwick College Chapter 6 Organic Chemistry
Carbon Of the millions of known compounds in our world, 95% have a single element in common: CARBON. What is so special about carbon?
Carbon Smallest member, and only nonmetal, of group 4A Forms 4 covalent bonds Forms single, double, and triple bonds Bonds to itself, forming chains and rings
Organic Chemistry The study of carbon-containing compounds and their chemistry is called organic chemistry. The properties of carbon-containing molecules determine the properties of the substance they compose.
Organic vs. Inorganic Early 1800s –Organic Compounds Came from living organisms Chemically fragile Unsuccessful synthesis... required a vital force? –Inorganic Compounds Came from the earth Chemically durable Successfully synthesized by 19 th -century chemists
Urea Synthesized by Friedrich Wohler in 1828 Organic, but synthesized from an inorganic compound Subsequent death of vitalism –The idea that life was somehow beyond physical laws was proven wrong. –Living organisms must follow the physical laws of the universe.
Two Major Types of Organic Compounds Hydrocarbons –Contain only carbon and hydrogen Functionalized Hydrocarbons –Hydrocarbons that contain additional atoms or groups of atoms called functional groups Both groups can be further divided into subfamilies.
The Hydrocarbon Family Alkanes –Only single bonds Alkenes –One or more double bonds Alkynes –One or more triple bonds Aromatic –Six-membered rings with alternating single and double bonds
Alkanes All carbon atoms connected by single bonds General molecular formula: C n H 2n+2 Simplest is methane, CH 4 Each atom attains an octet; the molecular geometry of methane is tetrahedral. Example of larger alkanes:
Polarity of Hydrocarbons Carbon-hydrogen bonds are mostly nonpolar but any polarity would be symmetrically arranged about the central carbon atom(s). Methane’s tetrahedral geometry makes it a nonpolar molecule. –All other hydrocarbons are nonpolar as well. Nonpolar substances are unable to mix with polar substances.
Structural Formulas Show the relative positions of atoms in a molecule Two-dimensional Similar to Lewis structures but dashes represent bonding electron pairs Condensed structural formulas are compactly written structural formulas. Example: Pentane (C 5 H 12 )
Naming Alkanes Straight chain alkanes are named with a base name reflecting the number of carbon atoms in the longest continuous chain and using the suffix -ane.
Concept Check 6.1 Give the molecular, structural, and condensed formulas for the straight-chained alkanes with seven and eight carbons and name them.
Concept Check 6.1 Solution C 7 H 16 : heptane C 8 H 18 : octane
Alkanes The most important property of the alkanes is their flammability, the combustion reaction between oxygen and the alkane that produces carbon dioxide and water.
Saturation Alkanes are saturated; they contain the maximum number of hydrogen atoms per carbon atom. Alkenes and alkynes are unsaturated. They contain at least one double or triple bond, respectively. They have fewer hydrogen atoms per carbon atom than alkanes.
Alkenes Flammable and nonpolar like alkanes Double bond makes them more chemically reactive than alkanes by addition across the double bond. Straight chain alkenes are named with a base name reflecting the number of carbon atoms in the longest continuous carbon chain and using the suffix -ene. This chain is numbered from the end giving the C-C double bond the lowest possible number Bananas exposed to ethene ripen faster.
Concept Check 6.2 Draw the structural formula for 1-hexene.
Concept Check 6.2 Solution The hex prefix indicates that there are six carbons. The –ene ending indicates that it is an alkene (contains a carbon-carbon double bond). The “1” indicates where the double bond begins (on carbon #1), with the longest continuous carbon chain numbered from the end giving the double bond the lowest number.
Alkynes Like alkenes, not commonly encountered directly Ethyne (acetylene) is used in welding torches. Straight chain alkynes are named with a base name depending on the number of atoms in the longest carbon chain with the suffix –yne and numbered from the end giving the C-C triple bond the lowest possible number.
Concept Check 6.3 Draw the structural formula for 1-hexyne.
Concept Check 6.3 Solution The hex prefix indicates that there are six carbons. The –yne ending indicates that it is an alkyne (contains a carbon-carbon triple bond). The “1” indicates that the triple bond begins on carbon #1, with the longest continuous carbon chain numbered from the end giving the triple bond the lowest number.
Isomers It is possible for organic compounds to share a molecular formula but have different structures based on the branching of the carbon chain. Isomers can differ in their physical and chemical properties.
Unsaturated Isomers Alkenes and alkynes exhibit isomerism based on the position of the multiple bond.
Naming Hydrocarbons: IUPAC Recommendations Alkanes –Determine the base name of the longest continuous carbon chain. –Consider branches to be substituents of the base chain. –Number the base chain beginning with the end closest to the first branch. –Order the name: Number of the substituent followed by a dash Name of the substituent Base name of the compound
Concept Check 6.4 Solution The longest continuous carbon chain has six carbons and is named hexane. It is numbered from the end giving the substituent the lowest possible number. Methyl substituent at carbon #3 The compound is named 3-methylhexane
Naming Hydrocarbons: IUPAC Recommendations When two or more substituents are present, number each and list them alphabetically. –Use a numbering system that contains the lowest possible numbers. –For two or more substituents on the same carbon, use that number twice. –Use prefixes to denote identical substituents.
Concept Check 6.5 Solution Heptane is the longest continuous carbon chain. Two methyls and an ethyl branching substituents Substituents named as 5-ethyl and 2,2-dimethyl according to their positions on the chain, then listed alphabetically in the name.
Naming Alkenes and Alkynes Similar to alkanes except for the addition of a number at the beginning to indicate the position of the multiple bond(s) 1-butene 4-methyl-2-pentene 2-pentyne5-ethyl-3-heptyne
Kekulé and Aromaticity Early structure elucidation –Carbon’s tendency toward four bonds Dreamed that he saw chains of six carbon atoms as snakes –One snake bit its own tail Proposed benzene as a ring of six carbon atoms Structure is still accepted today
Update on Kekulé’s Benzene Ring Kekulé proposed a ring containing alternating double and single bonds. The bonds in benzene have since been found to be all of the same length. Each bond is now considered to be midway between a double and a single bond. Modern representation is a circle within a hexagon.
The Benzene Ring Particularly stable When the ring contains substituents, it is called a phenyl ring. Also called aromatic ring due to the notable aroma of many compounds containing such a ring Two or more such rings fused together make polycyclic aromatic hydrocarbons.
Functionalized Hydrocarbons Basic hydrocarbon structures form a foundation for a major grouping of organic compounds. Contain additional atoms or groups of atoms called functional groups. Insertion of functional groups to a hydrocarbon dramatically alters its properties.
Representing Functionality Compounds containing the same functional group are called a family. Generic symbolism is R–FG where R is the hydrocarbon part of the molecule and FG is the functional group. –Symbol for an alcohol, R–OH. Functional groups help organize and classify organic compounds. Compounds with the same functional groups have similar chemical and physical properties.
Concept Check 6.6 For the following compound, identify the functional group the name of its family.
Concept Check 6.6 Solution For the following compound, identify the functional group the name of its family.
Chlorinated Hydrocarbons Found in pesticides, solvents, and refrigerant liquids One or more chlorine atoms substitute for one or more hydrogen atoms Lower flammability and reactivity than hydrocarbons
DDT Muller demonstrated DDT’s effectiveness against insects and relative non-toxicity to humans. Stability made it efficient Dramatically decreased malaria in many countries Muller awarded Nobel Prize in 1948 Resistance and bioamplification led to DDT’s ban.
CFCs Chlorofluorocarbons are a subfamily of chlorinated hydrocarbons. Chemically stable... Until they reach the high-energy sunlight in the upper atmosphere Ozone destruction led to bans.
Alcohols General formula: R–OH Addition of the –OH makes alcohols polar. Increased intermolecular attractive forces make alcohols liquids. Naming involves modifying the hydrocarbon name with an ending of -ol.
Other Alcohols Isopropyl alcohol is commonly known as rubbing alcohol. Methanol is toxic to the human liver. Ethanol is administered as an antidote.
Aldehydes and Ketones Commonly found in pleasant flavors and aromas Contain the carbonyl group: carbon double bonded to an oxygen atom
Formulas Aldehydes –General formula: RCHO, includes carbonyl group –Named according to length of the carbon chain with the ending of -al or -aldehyde –Methanal (formaldehyde) is the simplest aldehyde. Preservation of biological specimens
Formulas Ketones –Similar to aldehydes but have two R groups with the carbonyl –Names end in -one –Acetone is the simplest ketone. Fingernail polish remover
Carboxylic Acids Commonly found in sour foods General formula: RCOOH One oxygen atom is bonded as a carbonyl group (C=O), and the other is an –OH group.
Esters Esters have pleasant odors. General formula: R–COO–R′, where R can be a hydrocarbon or a hydrogen atom, R′ must be a hydrocarbon. Esters are named according to the relevant R and R′ groups, and have an –ate ending.
Ethers Ethers contain the functional group –O–. General formula: R–O–R′ where R and R′ are hydrocarbons. Named according to the R and R′ groups and given the ending -ether
Amines Amines are organic compounds that contain nitrogen. General formula: NR 3 (R can be a hydrocarbon or a hydrogen atom) Notable for disagreeable odors Named for R groups present and ending in -amine
Concept Check 6.7 Match each the following compounds with the following families: ketone, aldehyde, ester, carboxylic acid, alcohol, and amine.
Concept Check 6.7 Solution The functional groups are circled.
Chapter Summary Molecular Concept Organic vs. inorganic Hydrocarbons Alkanes Alkenes Alkynes IUPAC naming Other functional groups Societal Impact Organic compounds make our everyday lives possible. Hydrocarbons are the primary molecules our society uses for fuel.