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Organic Chemistry. 1 2 3 4 bonds. Topic 10.1.1 – 10.1.8. H O N C. What is organic chemistry?. study of carbon, the compounds it makes, and the reactions it undergoes over 16 million carbon-containing compounds are known
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Organic Chemistry 1234 bonds Topic 10.1.1 – 10.1.8 HONC
What is organic chemistry? • study of carbon, the compounds it makes, and the reactions it undergoes • over 16 million carbon-containing compounds are known • because the C-C single bond (348 kJ mol-1) and the C-H bond (412 kJ mol-1) are strong, carbon compounds are stable • carbon can form chains and rings
Homologous series/compounds (10.1.1) • related compounds that have the same functional group (groups of atoms found within molecules that are involved in the chemical reactions characteristic of those molecules)
differ from each other by a CH2 unit • can be represented by a general formula • examples: • CnH2n+2 (alkanes) or CnH2n (alkenes) or…
have similar chemical properties • have physical properties that vary in a regular manner as the number of carbon atoms increases • Example: the alkanes
Trends in boiling points of members of a homologous series (10.1.2) • melting point and boiling point increase with more carbon atoms • Why? • intermolecular forces increase • adding a CH2 adds more electrons • this increases the Van der Waal’s forces
empirical formula • simplest ratio of atoms in a molecule • molecular formula • actual numbers of atoms in a molecule
structural formula • unambiguously shows how the atoms are bonded together • can use condensedstructural formulas • bonds are omitted, repeated groups put together, side chains put in brackets • CH3CH2CH2CH2CH2CH3 • or even CH3(CH2)4CH3 • CH3CH(CH3)CH3
skeletal formula • not accepted in the IB for answers but often used in questions • every “corner” represents a carbon • hydrogens are implied
Isomers (10.1.4) • (structural) isomers: compounds with the same molecular formula but different structure (arrangement of atoms)
different isomers are completely different compounds • have different physical properties such as melting point and boiling point
Structural formulas for the isomers of non-cyclic alkanesup to C6(10.1.5) Alkanes • hydrocarbon chains where all the bonds between carbons are SINGLE bonds • CnH2n+2 • draw out and write the structural formulas for all isomers that can be formed by: • CH4 • C2H6 • C3H8 • C4H10 • C5H12 • C6H14 Richard Thornley 10.1.5 2:54
Monkeys Eat Peeled Bananas Naming the isomers (IUPAC) of non-cyclic alkanes up to C6(10.1.6) • Richard Thornley 3:35 • Determine the longest carbon chain • Use the prefix to denote the number carbons
use the suffix “-ane” to indicate that the substance is an alkane • number the carbons in the chain consecutively, starting at the end closest to a substituent (groups attached to the main chain/most busy end)
name and number the location of each substituent • the name of the substituent will be written before the main chain and will end with “–yl” (or just memorize the below) • CH3 is methyl • C2H5 is ethyl • C3H7 is propyl And with 2 or more side chains: • use prefixes di-, tri-, tetra-, to indicate when there are multiple side chains of the same type • use commas to separate numbers and hyphens to separate numbers or letters. • name the side chains in alphabetical order
How about C5H12? The isomers are: Pentane 2-methyl-butane 2,2-dimethyl propane
Nomenclature Practice Name this compound Step #1: For a branched hydrocarbon, the longest continuous chain of carbon atoms gives the root name for the hydrocarbon 1 9 carbons = nonane 2 4 3 5 6 7 8 9
Nomenclature Practice Name this compound 9 carbons = nonane 1 2 4 3 5 6 CH3 = methyl 7 chlorine = chloro 8 9 Step #2: When alkane groups appear as substituents, they are named by dropping the -ane and adding -yl.
Nomenclature Practice Name this compound Step #3: The positions of substituent groups are specified by numbering the longest chain of carbon atoms sequentially, starting at the end closest to the branching. 9 carbons = nonane 1 2 4 3 5 6 CH3 = methyl 7 chlorine = chloro 8 9 1 9 NOT 9 1
Nomenclature Practice Name this compound Step #4: The location and name of each substituent are followed by the root alkane name. The substituents are listed in alphabetical order (irrespective of any prefix), and the prefixes di-, tri-, etc. are used to indicate multiple identical substituents. 9 carbons = nonane 1 2 4 3 5 6 CH3 = methyl 7 chlorine = chloro 8 9 2-chloro-3,6-dimethylnonane
Alkenes Structural formulas for the isomers of the straight chain alkenesup to C6(10.1.7) • alkenes have a double bond between two or more of the carbons • CnH2n • draw out and write the structural formulas for all isomers that can be formed by each • C2H4 • C3H6 • C4H8 • C5H10 • C6H12 Richard Thornley 10.1.7 (1:37)
Naming the isomers (IUPAC) of straight chain alkenes up to C6(10.1.8) • suffix changes to “-ene” • when there are 4 or more carbon atoms in a chain, the location of the double bond is indicated by a number • begin counting the carbons closest to the end with the C=C bond • numbering the location of the double bond(s) takes precedence over the location of any substituents 1-butene 2-butene but-1-ene but-2-ene
Naming Practice!!! choose the correct ending ene
attach prefix (according to # of carbons) ene 1-hexene
ethyl methyl methyl determine name for side chains 1-hexene 1-hexene
ethyl methyl methyl attach name of branches alphabetically 2-ethyl-4-methyl-4-methyl-1-hexene
ethyl methyl methyl group similar branches 2-ethyl-4-methyl-4-methyl-1-hexene
ethyl methyl methyl group similar branches 2-ethyl-4,4-dimethyl-1-hexene or 2-ethyl-4,4-dimethyl hex-1-ene
propene 2,4-dimethyl-2-pentene 2,4-dimethyl pent-2-tene 2-butene
a) 3,3-dimethyl-1-pentene b) same C H 3 C H C C C H C H C H 3 3 C H 3 c) 4,5 dimethyl-2-hexene