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Chapter 6

CH. 6 ORGANIC CHEM.docx

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Department
Chemistry
Course
CHEM 1100
Professor
Kim Bolton
Semester
Winter

Description
CHAPTER 6 ORGANIC CHEMISTRY Carbon • 95% of compounds contain the element carbon • Carbon is the smallest member and the only non-metal in group 4A of the periodic table • It has 4 valence electrons and in its compounds forms 4 covalent bonds • It can form single, double or triple bonds • Carbon can also bond with itself • Carbons great versatility in bonding allows carbon to form a molecular framework with almost endless possibilities • Other elements, especially hydrogen, oxygen, nitrogen, sulfur and chlorine can incorporate into framework and add more variety • Organic chemistry the chemistry of carbon-containing compounds • Many organic compounds are found in living organisms A Vital Force • In 1800s scientists knew there were 2 types of chemical compounds: organic and inorganic • Organic compounds came from living organism and were chemically fragile (easily decomposed with heat) • Inorganic compounds came from the earth and were chemically durable (difficult to decompose) • Many scientists believed then that living organisms contained a vital force that allowed them to overcome ordinary physical laws and produced organic compounds  Proved wrong – living organisms must follow the physical laws of the universe • The chemistry of living organisms is biochemistry • Many organic compounds have uses that are not necessarily related to their biological origins  Most of our fuels are composed of organic compound that originated from prehistoric plant and animal life The Simplest Organic Compounds: Hydrocarbons • All organic compounds can be divided into 2 major types • Hydrocarbons are compound containing only carbon and hydrogen • Functionalized hydrocarbons are hydrocarbons with additional atoms or groups of atoms – called functional groups – incorporated into their structure CHAPTER 6 ORGANIC CHEMISTRY • The hydrocarbon family can be further divided into 4 subfamilies, 3 which depend on whether carbon-carbon bonds are single, double, or triple bonds – known as alkanes • The 4 subfamily is aromatic hydrocarbons contains a 6-carbon ring structure called an aromatic ring Alkanes: Gasoline and Other Fuels • Alkanes are hydrocarbons in which all carbon atoms are connected by single bonds • Have general formula C Hn 2n+2 where n represents the number of carbon atoms in the molecule • The simplest alkane is methane (CH ) 4  Carbon forms 4 single covalent bonds with 4 hydrogen atoms  The carbon atom attains an octet, and each hydrogen attains a duet – methane is stable  Geometry is tetrahedral because carbon has 4 electron groups and no lone pairs  Carbon and hydrogen have only slightly different electronegativities, making the bonds between them mostly nonpolar  Any slight polarity present in each bond is canceled by the tetrahedral shape of the molecule making methane a nonpolar molecule • Every other hydrocarbon is also nonpolar resulting in the inability of hydrocarbons to mix with polar substances such as water CHAPTER 6 ORGANIC CHEMISTRY • In organic chemistry we often use structural formulas to show the relative positions of atoms in a molecule  Dashes represent bonding electron pairs, and lone pairs are usually left out • Carbon must always have 4 bonds, and hydrogen must always form only one Alkanes N Name Molecular Formula Condensed Structural Formula N = Methan CH 4 CH 4 1 e N = Ethane C2H 6 CH 3H 3 2 N = Propan C3H 8 CH 3H C2 3 3 e N = Butane C H CH CH CH CH 4 10 3 2 2 3 4 N =5 Pentan C5H 12 CH 3H C2 CH2CH 2 3 e N = Hexane C6H 14 CH 3H C2 CH2CH 2H 2 3 6 N = Heptan C7H 16 CH 3H C2 CH2CH 2H C2 2 3 7 e N = Octane C H CH CH CH CH CH CH CH CH 8 18 3 2 2 2 2 2 2 8 3 • Straight-chain alkanes – those with no branches – are named with a base name, which depends on the number of atoms in the chain and suffix –ane Base Names for Hydrocarbons No. C atoms Base Name 1 Meth 2 Eth 3 Prop 4 But 5 Pent 6 Hex CHAPTER 6 ORGANIC CHEMISTRY 7 Hept 8 Oct 9 Non 10 dec Properties and Uses of Alkanes • The boiling point of alkanes increases with increasing carbon chain length • Alkanes with one to four carbon atoms are gases at room temperature and are used as fuels • Alkanes with 5 to 30 carbon atoms are liquids, many of which serve as the major components of gasoline and other liquid fuels • Alkanes with 20 to 40 carbon atoms are thick liquids that compose lubricants and oils • Alkanes with higher numbers of carbon atoms compose substances such as petroleum jelly and candle wax • Alkanes are flammable – they burn oxygen and give off heat making them good energy sources • Combustion reaction certain compounds, especially hydrocarbons, combine with oxygen to produce certain products, usually carbon dioxide and water Alkenes and Alkynes • Alkenes and alkynes are hydrocarbons that contain at least one double or triple bond • Alkenes = C n 2n • Alkynes = C H n 2n-2 • They have fewer hydrogen atoms per carbon atom than alkanes are referred to as unsaturated hydrocarbons • Alkanes are saturated hydrocarbons, they are saturated with H atoms; have the maximum number of hydrogen atoms per carbon atom • Simplest alkene is ethane, the geometry of ethane is trigonal planar  Each carbon atom forms 4 bonds, but there is a double bond between the two carbon atoms • An alkene can be derived from an alkane simply by removing 2 hydrogen atoms from adjacent carbon atoms and inserting a double bond Alkenes CHAPTER 6 ORGANIC CHEMISTRY N Name Molecular formula Condensed structural formula N=2 Ethene C 2 4 CH 2CH 2 N=3 Propene C 3 6 CH 2CHCH 3 N=4 1-Butene C 4 8 CH 2CHCH CH 2 3 N=5 1-Pentene C 5 10 CH 2CHCH CH 2H 2 3 • Alkenes are flammable and nonpolar • Their double bond makes them susceptible to the addition of other atoms • A common reaction of alkenes is the addition of substitutes across the double bond • Alkynes can be derived from alkenes by removing 2 additional hydrogen atoms from the 2 carbon atoms on either side of the double bond and placing a triple bond between them N Name Molecular Condensed structural formula formula N=2 Ethyne C2H 2 CH≡CH N=3 Propyne C3H 4 CH≡CCH 3 N=4 1-butyne C H CH≡CCH CH 4 6 2 3 N=5 1-pentyne C5H 8 CH≡CCH CH2CH 2 3 Isomers • Carbon atoms form long, straight chains as well as branched structures • Molecules that have the same molecular formula but different structures are called isomers • Isomers have different properties from each other and can be distinguished by inspecting their structural formulas • Alkenes and alkynes form another kind of isomerism based on the position of the double or triple bond • Since the double or triple bond is in a different position, the molecules are different, however it still has the same molecular formula • The different structures have different effects CHAPTER 6 ORGANIC CHEMISTRY • Ex. Progesterone make pregnancy possible, while THC found in marijuana alters the way the brain processes stimuli Naming Hydrocarbons 1. Select the longest continuous chain, count the number of carbon atoms in the chain and determine the base name (base name – ane, ene, or yne) 2. Consider every branch from the longest continuous chain to be a substituent of the base chain. Name each substituent according to the number of carbon atoms in the substituent; however change the –ane ending to –yl 3. Number the base chain beginning with the end closest to the branching and assign a number to each substituent (position number-step 2) 4. Finally write the name of the compound in the following order: the number of the substituent followed by a dash, the name of the substituent, and then the base name of the compound Additional steps: 5. When 2 or more substituents are present, give each one a number and list them alphabetically. If 2 or more numberings are possible, choose the set that contains the lowest number 6. When 2 or more substituents are on the same carbon use that number twice 7. When 2 or more substituents are identical, so indicate by using the prefixes di-, tri-, tetra-. Separate the numbers indicating their positions from each other using a comma Alkenes and Alkynes • Named similar to alkanes except for addition of a number at the beginning to indicate the position of the double or triple bond and a change from –ane to –ene or –yne in the base name • The base chain is
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