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Chapter 24 From Petroleum to Pharmaceuticals. 24.1 Petroleum Refining and the Hydrocarbons 24.2 Functional Groups and Organic Synthesis 24.3 Pesticides and Pharmaceuticals. IR Tutor and Infrared Spectroscopy. Hydrocarbons. Aliphatic. Aromatic. Hydrocarbons. Aliphatic. Aromatic. Alkanes.
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Chapter 24 From Petroleum to Pharmaceuticals 24.1 Petroleum Refining and the Hydrocarbons 24.2 Functional Groups and Organic Synthesis 24.3 Pesticides and Pharmaceuticals IR Tutor and Infrared Spectroscopy
Hydrocarbons Aliphatic Aromatic
Hydrocarbons Aliphatic Aromatic Alkanes Alkenes Alkynes
H H H H C C H H Hydrocarbons Alkanes are hydrocarbons in which all of the bonds are single bonds. Aliphatic Alkanes
H H C C H H Hydrocarbons Alkenes are hydrocarbons that contain at least one carbon-carbon double bond. Aliphatic Alkenes
HC CH Hydrocarbons Alkynes are hydrocarbons that contain a carbon-carbon triple bond. Aliphatic Alkynes
H H H H H H Hydrocarbons The most common aromatic hydrocarbons are those that contain a benzene ring. Aromatic
Reactive Sites in Hydrocarbons The Functional Group Concept
Functional Group a structural unit in a molecule responsible for itscharacteristic chemical behavior and its IR spectroscopic characteristics
R—H R—X Alkanes functional group is a hydrogen atom the reaction that takes place is termed a substitution one of the hydrogens is substitutedby some other atom or group, X
R—H R—X H H H H Cl H H H C C C C H H H H Alkanes functional group is a hydrogen the reaction that takes place is substitution one of the hydrogens is substituted by some other atom or group + HCl + Cl2
Functional Groups in Hydrocarbons alkanes RH alkenes RH, double bond alkynes RH, triple bond aromatics ArH, double bond
Families of organic compounds and their functional groups Alcohols ROH Alkyl halides RX (X = F, Cl, Br, I) Amines primary amine: RNH2 secondary amine: R2NH tertiary amine: R3N Ethers ROR
O O C C Many classes of organic compounds contain a carbonyl group R Carbonyl group Acyl group
O O C C Many classes of organic compounds contain a carbonyl group H R Carbonyl group Aldehyde
O O C C Many classes of organic compounds contain a carbonyl group R' R Carbonyl group Ketone
O O C C Many classes of organic compounds contain a carbonyl group OH R Carbonyl group Carboxylic acid Not a ketone-alcohol!
O O C C Many classes of organic compounds contain a carbonyl group OR' R Ester Carbonyl group Not a ketone-ether!
O O C C Many classes of organic compounds contain a carbonyl group NH2 R Amide Carbonyl group Note a ketone-amine!
Alkanes General formula for an alkane CnH2n+2 Introduction to Alkanes: Methane, CH4 Ethane, C2H6 Propane, C3H8
The simplest alkanes Methane (CH4) CH4 Ethane (C2H6) CH3CH3 Propane (C3H8) CH3CH2CH3 bp -160°C bp -89°C bp -42°C No isomers possible for C1, C2, C3 hydrocarbons
Isomeric Alkanes: The Butanes C4H10 General formula for any butane Isomers: same composition, different structures at the constitutional or stereochemical levels
C4H10 n-Butane (bp -0.4°C) Isobutane (bp -10.2°C) CH3CH2CH2CH3 (CH3)3CH
Higher n-Alkanes Pentane (C5H12) and Beyond CnH2n+2 n > 4
CnH2n+2 n > 4 CH3CH2CH2CH2CH3 n-Pentane CH3CH2CH2CH2CH2CH3 n-Hexane CH3CH2CH2CH2CH2CH2CH3 n-Heptane
C5H12 (CH3)2CHCH2CH3 CH3CH2CH2CH2CH3 Isopentane n-Pentane (CH3)4C Neopentane
How many isomers? The number of isomeric alkanes increases as the number of carbons increase. There is no simple way to predict how many isomers there are for a particular molecular formula.
Table 2.3 Number of Constitutionally Isomeric Alkanes CH4 1 C2H6 1 C3H8 1 C4H10 2 C5H12 3 C6H14 5 C7H16 9
Table 2.3 Number of Constitutionally Isomeric Alkanes CH4 1 C8H18 18 C2H6 1 C9H20 35 C3H8 1 C10H22 75 C4H10 2 C15H32 4,347 C5H12 3 C20H42 366,319 C6H14 5 C40H82 62,491,178,805,831 C7H16 9 (~6 x 1013 isomers!)
C6H6 Isomers How many isomers with the composition C6H6 can you draw?
C6H6 Isomers: How many isomers with the compositionC6H6 can you draw?
Structure of Ethylene bond angles: H-C-H = 117° H-C-C = 121° bond distances: C—H = 110 pm C=C = 134 pm planar
Bonding in Ethylene Framework of s bonds Each carbon is sp2 hybridized s s s s s
Bonding in Ethylene Each carbon has a half-filled p orbital
Bonding in Ethylene Side-by-side overlap of half-filled p orbitals gives a p bond which makes it very difficult to rotate about the C=C bond
Isomers Isomers are different compounds thathave the same composition (numbers and kinds. of atoms). Since the compounds are different, they must have different structures in the way the atoms are connected or arranged in space
Isomers Constitutional isomers Stereoisomers
Isomers Constitutional isomers Stereoisomers same connectivity; different arrangementof atoms in space different connectivity
Isomers Constitutional isomers Stereoisomers consider the isomeric alkenes of molecular formula C4H8
H3C H CH2CH3 H C C C C H3C H H H H3C CH3 H H3C C C C C H H H CH3 1-Butene 2-Methylpropene trans-2-Butene cis-2-Butene
H3C H CH2CH3 H C C C C H3C H H H H3C CH3 C C H H 1-Butene 2-Methylpropene Constitutional isomers cis-2-Butene
H3C CH3 H H3C C C C C H H H CH3 Same connections, different atomic positions in space Stereoisomers trans-2-Butene cis-2-Butene
Isomers constitutional isomers stereoisomers
Isomers constitutional isomers stereoisomers enantiomers (optical) geometric isomers (cis/trans) Chiral structures