Organic Chemistry Chapter 22. Vocabulary Organic Chemistry Hydrocarbons Saturated Unsaturated...
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Transcript of Organic Chemistry Chapter 22. Vocabulary Organic Chemistry Hydrocarbons Saturated Unsaturated...
Organic ChemistryChapter 22
Vocabulary • Organic Chemistry• Hydrocarbons• Saturated• Unsaturated• Alkanes• Alkenes• Alkynes• Cis-trans isomerism
• Carbonyl group• Ketones• Aldehydes• Carboxylic acids• Carboxyl group• Ester• Ether• Amine
Saturated vs. UnsaturatedHydrocarbons
• Hydrocarbons are molecules composed of carbon & hydrogen– Each carbon atom forms 4 chemical bonds– A saturated hydrocarbon is one where all C - C
bonds are “single” bonds & the molecule contains the maximum number of H-atoms
– An unsaturated hydrocarbon is one where at least 1 C=C bond is double.
Prefixes for # of CarbonsPrefixes for # of Carbons
11 MethMeth 66 HexHex
22 EthEth 77 HeptHept
33 PropProp 88 OctOct
44 ButBut 99 NonNon
55 PentPent 1010 DecDec
AlkanesAlkanes• Hydrocarbon chains where all the bonds between Hydrocarbon chains where all the bonds between
carbons are SINGLE bondscarbons are SINGLE bonds• Name uses the ending –Name uses the ending –aneane• Examples: MethExamples: Methaneane, Prop, Propaneane, But, Butaneane, Oct, Octaneane
• Formula: (CnH2n+2)
Straight-Chain Alkanes• Straight-chain alkanes contain any
number of carbon atoms, one after the other, in a chain pattern - meaning one linked to the next (not always straight)C-C-C C-C-C-C etc.
Writing/drawing compounds
Line formula
Normal vs Branched Alkanes• NORMAL alkanes consist of
continuous chains of carbon atoms
• Alkanes that are NOT continuous chains of carbon atoms contain branches
• The longest continuous chain of carbons is called the parent chain
CH3
CH2CH2
CH2CH3
CH3
CH2CH
CH3
CH3
EndingsEndings• Attached carbon groups (substituents) end in Attached carbon groups (substituents) end in
–yl–yl– MethMethylyl CH CH33 - -– EthEthylyl CHCH33CHCH22--– PropPropylyl CH CH33CHCH22CHCH2 2 – –
3-ethylpentane
Names of branchesNames of branches
• Carbon (alkCarbon (alkylyl) groups) groups– MethMethylyl CH CH33 - -– EthEthylyl CHCH33CHCH22--– PropPropylyl CH CH33CHCH22CHCH2 2 ––
Branched-Chain Alkanes• Rules for naming –1. Longest C-C chain is parent2. Number so branches have lowest #3. Give position number to branch4. Prefix (di, tri) more than one branch5. Alphabetize branches (not prefix)6. Use proper punctuation ( - and , )
Designate the LocationDesignate the Location
• Designate the location (number of the carbon on the parent chain) for each attached group
1 2 3 4 5
2-methyl
Name this compound
• 3,3-dimethylhexane
Some Simple AlkanesSome Simple Alkanes
• 2-methylpentane2-methylpentane
• 3-ethylhexane3-ethylhexane
• 2,2-dimethylbutane2,2-dimethylbutane
• 2,3-dimethylbutane2,3-dimethylbutane
Branched-Chain Alkanes• From the name, draw the structure, in a
right-to-left manner:1. Find the parent, with the -ane2. Number carbons on parent3. Identify substituent groups (give lowest
number); attach4. Add remaining hydrogens
Example 1: 2,2-dimethylpentane2,2-dimethylpentane• The parent chain is indicated by
the ROOT of the name - “pentanepentane”. This means there are 5 carbons in the parent chain.
CH3
CH2CH2
CH2CH3
• “dimethyldimethyl” tells us that there are TWO methyl branches on the parent chain. A methyl branch is made of a single carbon atom.
• “2,22,2-” tell us that BOTH methyl branches are on the second carbon atom in the parent chain.
CH31
CCH23
CH2
4
CH35
CH3
CH3
1
2
3
4
5
Example 2: 3-ethyl-2,4-dimethylheptane3-ethyl-2,4-dimethylheptane• The parent chain is indicated by
the ROOT of the name - “heptaneheptane”. This means there are 7 carbons in the parent chain.
CH3
CH2CH2
CH2CH2
CH2CH3
• “2,4-dimethyl2,4-dimethyl” tells us there are TWO methyl branches on the parent chain, at carbons #2 and #4.
• “3-ethyl3-ethyl-” tell us there is an ethyl branch (2-carbon branch) on carbon #3 of the parent chain.
1
2
3
4
5
76
CH3
CHCH
CHCH2
CH2CH3
CH2
CH3
CH3 CH3
Example 3: 2,3,3-trimethyl-4-propyloctane2,3,3-trimethyl-4-propyloctane• The parent chain is indicated by
the ROOT of the name - “octaneoctane”. This means there are 8 carbons in the parent chain.
• “2,3,3-trimethyl2,3,3-trimethyl” tells us there are THREE methyl branches - one on carbon #2 and two on carbon #3.
• “4-propyl4-propyl-” tell us there is a propyl branch (3-carbon branch) on carbon #4 of the parent chain.
1
2
34
5
7
6
8
1
23
45
7
6
8
CHC
CHCH2
CH2
CH2CH3
CH3
CH3
CH3
CH3CH2
CH2
CH3
Example 4: Name the molecules shown!
• parent chain has 5 carbons - “pentane”
• two methyl branches - start counting from the right - #2 and #3
• 2,3-dimethylpentane2,3-dimethylpentane
CH3
CH2
CHCH
CH3
CH3
CH3
• parent chain has 8 carbons - “octane”• two methyl branches - start counting
from the left - #3 and #4• one ethyl branch - #5• name branches alphabetically
3,4-dimethyl3,4-dimethyl
4433
octaneoctane
55
5-ethyl-5-ethyl-
Draw 2,2,4-trimethylpentane
Structural Isomerism• Structural isomers are
molecules with the same chemical formulas but different molecular structures
CH3
CH2CH2
CH2CH3
CH3
CH2CH
CH3
CH3
n-pentane, C5H12
2-methlbutane, C5H12
• However, carbons in butane (CHowever, carbons in butane (C44HH1010) can be ) can be arranged in two ways; four carbons in a row (linear arranged in two ways; four carbons in a row (linear alkane) or a branching (branched alkane). These alkane) or a branching (branched alkane). These two structures are two isomers for butane.two structures are two isomers for butane.
Your TurnYour Turn• Draw all possible structural isomers of C5H12
Practice
IUPAC Rules for Naming Branched Alkanes
– Find and name the parent chainFind and name the parent chain in the hydrocarbon - this forms the root of the hydrocarbon name
– Number the carbon atoms in the parent chainNumber the carbon atoms in the parent chain starting at the end closest to the branching
– Name alkane branchesName alkane branches by dropping the “ane” from the names and adding “yl”. A one-carbon branch is called “methyl”, a two-carbon branch is “ethyl”, etc…
– When there are more than one type of branch (ethyl and methyl, for example), they are named alphabeticallyalphabetically
– Finally, use prefixesuse prefixes to indicate multiple branches
CLASSWORK ASSIGNMENTCLASSWORK ASSIGNMENT• Review section 22-1Review section 22-1
– make notes on NONMENCLATURE OF ALKANES and CYCLIC ALKANES
– Pay attention to sample exercises!
Alkenes & AlkynesAlkenes & Alkynes• Alkenes are
hydrocarbons that contain at least one carbon-carbon double double bondbond
• Alkynes are hydrocarbons that contain at least one carbon-carbon triple triple bondbond
• The suffix for the parent chains are changed from “ane” to “ene” and “yne”– e.g. ethene, propyne
• the BONDS are numbered like branches so that the location of the multiple bond may be indicated
Alkenes & Alkynes: Examples
CH2 CH2 CHCH CH2 C
H
CH3
C16
CH
CH3 CH2 CH
CH2
CH3C C CH2CH3
CH3
ethene ethyne propene
propyne butene 2-pentyne
Aromatic Hydrocarbons Aromatic Hydrocarbons CycloalkanesCycloalkanes
• A cycloalkane is made of a hydrocarbon chain that has been joined to make a “ring”.
CH3
CH2
CH3 CH2
CH2
CH2
n-propaneC3H8
cyclopropaneC3H6
60° bond angleunstable!!
109.5° bond angle
•Note that two hydrogen atoms were lost in forming the ring!
Aromatic Hydrocarbons Aromatic Hydrocarbons CycloalkanesCycloalkanes
• The two ends of the carbon chain are attached in a ring in a cyclic hydrocarbon– named as “cyclo- ____”
Aromatic Compounds and BenzeneAromatic Compounds and Benzene
Aromatic compounds contain benzene.
Benzene, C6H6 , is represented as a six carbon ring with 3 double bonds.
Two possible resonance structures can be drawn to show benzene in this form.
H
H
H
H
H
H
HH
H
H
H
H
Aromatic HydrocarbonsAromatic Hydrocarbons• Benzene derivatives can have two or more
substituents:– 1,2-dimethylbenzene– 1,3-dimethylbenzene– 1,4-dimethylbenzene
• Can use ortho for 1,2; meta for 1,3; and para for 1,4 (page 711)
C
C
CC
IsomersIsomersWith organic compounds
Isomers• There is a lack of rotation around a carbon
to carbon multiple bond– Two possible arrangements:
1. trans configuration - substituted groups on opposite sides of double bond
2. cis configuration - same side
Substituted groups are on opposite sides of the double bond (in this case, one is above, the other is below)
Substituted groups are on the same side of the double bond (in this case, both are above)
Geometric Isomers
Trans-2-butene
Cis-2-butene
Cis-Trans Isomers - Examples
Cl Cl
CH1
CH2
2
CH3
CH34CH25
CH3
6
cis-1,3-dimethylcyclobutanecis-1,3-dimethylcyclobutane
cis-1,2-dichlorocyclohexanecis-1,2-dichlorocyclohexane
trans-1-ethyl-2-methylcyclopropanetrans-1-ethyl-2-methylcyclopropane
ReactionsReactionsWith organic compoundsWith organic compounds
AlkanesAlkanes1. Combustion Combustion reactions
2C2H6(g) + 7O2(g) 4CO2(g) + 6H2O(g)
2. SubstitutionSubstitution reactionsCH4 + Cl2 CH3Cl + HCl
Methane chloromethane
3. DehydrogenationDehydrogenation reactionsCH3CH3 CH2=CH2 + H2
Ethane ethene
hv
500C
Alkenes & AlkynesAlkenes & Alkynes1. Addition Addition reactions
a. Hydrogenationa. Hydrogenation
CH2 =CHCH3+ H2 CH3CH2CH3Propene Propane
b. Halogenation b. Halogenation CH2 =CHCH2CH2CH3 + Br2 CH2 BrCHBrCH2CH2CH3
Pentene 1,2-dibromopentene
c. Polymerizationc. PolymerizationSmall molecules = large molecules
Catalyst
AromaticAromatic1. Substitution Substitution reactions
+ Cl2 + HClCatalyst = FeCl3
Functional GroupsFunctional GroupsWith organic compoundsWith organic compounds
Functional GroupsFunctional Groups
Functional group:Functional group: an atom or group of atoms within a molecule
Functional Groups
AlcoholsAlcohols
contain an -OH (hydroxylhydroxyl) group
H-C-C-O-H
H
H
H
H::-C-O-H
Ethanol(an alcohol)
Functionalgroup
CH3-CH2-OH CH3CH2OHor
Halides & Carboxylic AcidsHalides & Carboxylic Acids
contain an -X (HalogenHalogen) groupF, Cl, Br, I, At
contain a carboxyl (-COOH) groupcarboxyl (-COOH) group
C O
O
H CH3-C-O-HO
CH3COOH CH3CO2H
: ::: or or
Acetic acid(a carboxylic acid)
Functionalgroup
Aldehydes and KetonesAldehydes and Ketones
contain a carbonyl (C=O) groupcarbonyl (C=O) group
C H
O
CH3-C-H
O
CH3-C-CH3
O
C
O
Functionalgroup
Acetaldehyde(an aldehyde)
Acetone(a ketone)
Functionalgroup
AminesAmines contain an amino groupamino group; nitrogen bonded to
one, two, or three carbon atoms– an amine may by 1°, 2°, or 3°
CH3 N H
H
CH3 N H
CH3
CH3 N CH3
CH3
Methylamine(a 1° amine)
Dimethylamine(a 2° amine)
Trimethylamine(a 3° amine)
: : :
Esters & EthersEsters & Ethers Ester:Ester: trapped carboxylic acid
Ether: Ether: Trapped oxygen
C O
O
Functionalgroup
CH3-C-O-CH2-CH3
Ethyl acetate(an ester)
::
: :O
BranchesCnH2n+2 Alkane CnH2n+1 Alkyl group
CH4 methane CH3 Methyl
C2H6 ethane C2H5 ethyl
C3H8 propane –C3H7 propyl
CH3CHCH3 methylethyl
Functional Group
General Formula
Name Examples
saturated ring CnH2n cycloalkane cyclohexane
-X -RX haloalkane chloroethane
R-O-R’ ether ethoxyethane
-OHROH
alkanol ethanol
(-CHO)
RCHO
alkanal ethanal
-NH2 RNH2 amine methylamine
alkanone butan-2-one
-COOH RCOOH alkanoic acid ethanoic acid
-COOR’ RCOOR’ ester methyl ethanoate
C
O
C R'R
O
Naming
Naming
Naming