Topic 10: Organic Chemistry

SWBAT: Identify different classes of organic compounds Describe why organic chemistry is so important Use IUPAC naming conventions to name alkanes Agenda Intro to Orgo Organic Nomenclature

Organic Chemistry The study of carbon based compounds Because carbon has 4 valence electrons, she can make 4 bonds which produces many straight- chain, branched, or cyclic structures Just like taxonomy in biology, organic chemists use a system to group & name organic compounds that share important features & patterns of reactions You need organic chemistry if you want to go into: forensic chemistry, food science, pharmaceuticals, medicine, environmental science, science professor, R&D scientist

IUPAC

Homologous Series A series of compounds that can be grouped together based on similarities in their structure & reactions Have the same general formula which varies by one member to another by one CH 2 group Examples are alkanes, alkenes, alkynes The physical properties of the members of a homologous series change gradually as the length of the carbon chain increases

NameFormulaCondensed structural formulastructural formulaBoiling point °C methaneCH ethaneC2H6C2H6 CH propaneC3H8C3H8 CH 3 CH 2 CH butaneC 4 H 10 CH 3 CH 2 CH 2 CH pentaneC 5 H 12 CH 3 CH 2 CH 2 CH 2 CH 3 36 hexaneC 6 H 14 CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 69 Alkanes C n H 2n+2

Homologous Series The trend in boiling points results from increasingly strong IMF’s Trends in increasing density and viscosity with carbon chain lengths are well understood by the petrochemical industry

Chemical formulas of organic compounds Structure of an organic cmpd can be represented in several different ways Lewis dot structures are useful to visualize valence e - s present in simple cmpds & ions Empirical formula represents the simplest ratio of atoms present in a molecule Molecular formula describes the actual number of atoms present in the molecule

Chemical formulas of organic compounds Structural formulas take 3 forms: Full – 2D representations showing all the atoms, bonds, & their positions relative to one another in a cmpd Condensed – all the atoms and their relative positions are represented but the bonds are omitted Skeletal – most basic representation of the structural formula where the carbon & hydrogen atoms are not shown but the end of each line & each vertex represents a carbon atom, atoms present in functional groups are included propanol CH 3 CH 2 CH 2 OH

Nomenclature of Organic Compounds

Nomenclature of Alkanes 1)Examine the structure & determine the longest continuous carbon chain, this provides the root name for the alkane Length of carbon chain Name 1Meth- 2Eth- 3Prop- 4But- 5Pent- 6Hex- To remember the 1 st four: MEPB The rest are the same prefixes previously learned for inorganic nomenclature

Nomenclature of Alkanes 2)if alkyl substituents are present, creating a branch, the name for the branch will be determined by the # of carbons

Nomenclature of Alkanes 3)When numbering the longest carbon chain, the position of any substituent must be the lowest numbered carbon Correct numbering Incorrect numbering

Nomenclature of Alkanes 4)When there are several different substituents, arrange them in alphabetical order prior to the root name 3-ethyl-2-methylpentane

Nomenclature of Alkanes 5)Use a comma to separate numbers 6)Use a hyphen to separate numbers and letters 7)The number of multiple substituents of the same type is indicated by the same prefixes for inorganic naming (1-mono, 2-di, 3-tri…) 8)Successive words are merged into one word

Nomenclature of Alkanes hexane 2-methylpentane 3-methylpentane

hexane 2-methylpentane 3-methylpentane These compounds are structural isomers – cmpds that have the same chemical formula but a different structural formula. Isomers have unique physical and chemical properties

Nomenclature of Alkanes 2,2-dimethylbutane 2,3-dimethylbutane

*Note* Just because a carbon chain is drawn a certain way does NOT mean it’s drawn so the longest chain is horizontal – always count your carbons! This hydrocarbon is named 3,3-dimethylpentane NOT 2,2- diethyl propane

Name these alkanes 2-methylhexane 3-methylhexane 2,3,4-trimethylhexane 2,3,3-trimethylhexane 3-ethyl-2-methylhexane cyclohexane

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