Post on 19-Dec-2015
Chapter 13 | Slide 2 of 70
Unsaturated Hydrocarbons
• AlkANES– Hydrocarbons in which all of the carbon-carbon bonds
are _____________ bonds
• AlkENES– Hydrocarbons in which at least one of the carbon-
carbon bonds is a ____________ bond
• AlkYNES– Hydrocarbons in which at least one of the carbon-
carbon bonds is a ______________ bond
Chapter 13 | Slide 3 of 70
Properties of Alkenes and Alkynes
• Similar to those of alkanes– .– .– .
• .
Chapter 13 | Slide 4 of 70
Alkenes
• Draw the structures of the monounsaturated alkenes with 4, 5, and 6 carbons
• What is the relationship between the number of carbons and the number of hydrogens in these alkenes?– .
Chapter 13 | Slide 5 of 70
Alkynes
• Draw the structures of the monounsaturated alkynes with 4, 5, and 6 carbons
• What is the relationship between the number of carbons and the number of hydrogens in these alkenes?– .
Chapter 13 | Slide 6 of 70
Bond Angles in Alkenes and Alkynes
• According to VSEPR theory:– The four groups bonded to
carbon atoms in single bonds are at angles of ____________________
– The three groups bonded to carbon atoms in a double bond are at angles of ______________________
– The two groups bonded to carbon atoms in a triple bond are at angles of _____________________
Chapter 13 | Slide 7 of 70
→Fig. 13.1 In ethene, the atoms are in a flat rather than a tetrahedral arrangement. Note the shapes using space filling molecular models.
Unsaturated Hydrocarbons cont’d
Chapter 13 | Slide 8 of 70
σ and π Bonds
• A single bond between 2 carbon atoms is called a sigma (σ) bond.
• The second bond that forms in a double bond is called the pi (π) bond.
• The third bond that forms a triple bond is also called the pi (π) bond.
• There is π bonding in all double and triple bonds between two carbon atoms.
• π bonds are more reactive than sigma bonds.
Chapter 13 | Slide 9 of 70
Carbon-carbon double bonds Names end in -___________
H2C=CH2
H2C=CH-CH3
Alkenes
Chapter 13 | Slide 10 of 70
Carbon-carbon triple bonds Names end in _____________
HCCH
HCC-CH3
Alkynes
Chapter 13 | Slide 11 of 70
Naming
• Step 1:– Name ___________________________.
• Find the longest continuous carbon chain that contains the multiple bond.
• Name that chain with the __________ suffix if it has a double bond.
• Name the chain with the _______ suffix if it has a triple bond.
CH3CH2CH2
CH3CH2CH2
C
Chapter 13 | Slide 12 of 70
Naming
• Step 2:– Number the carbon atoms.
• Begin numbering _____________________________
CH3CH2CH2
CH3CH2CH2
C
Chapter 13 | Slide 13 of 70
Naming
• Step 2:– Number the carbon atoms.
• If the multiple bond is the same distance from each end of the molecule, begin _________________________
CH3CHCH CHCH2CH3
CH3
1 2 3 4 5 66 5 4 3 2 1 ???
Chapter 13 | Slide 14 of 70
Naming
• Step 3:– Use ___________________________________
_________________to designate multiple bond position.
– List the substituents ________________(with numbers to designate position).
CH3CH2CH2
CH3CH2CH2
C12
345
Chapter 13 | Slide 15 of 70
Naming
• Step 3:– Use “di”, “tri”, “tetra”, etc. to designate _________
_____________________________
CH3CH2CH2
CH3CH2CH2
C12
345
pentene2-ethyl
1-
Chapter 13 | Slide 16 of 70
Name these alkenes.
CH3CHCH CHCH2CH3
CH3
CH3CH2CH2
CH3CH CHC
CH2 CCH CH2
CH3
Chapter 13 | Slide 18 of 70
Naming cycloalkenes
• Number the double bond ______________.• The first substituent possesses __________
______________________.
Chapter 13 | Slide 20 of 70
Write the IUPAC name for each of the following unsaturated compounds:
A. CH3CH2CCCH3
CH3
B. CH3C=CHCH3 C.
Learning Check
Chapter 13 | Slide 21 of 70
Learning Check
• Draw the structures that correspond to the following names
– 4-methyl-1-hexene– 1,3-cyclohexadiene– 4,4,5-trimethyl-2-heptene– 4-chloro-1-pentyne– 5-fluoro-4-ethyl-2-hexyne
Chapter 13 | Slide 22 of 70
Isomerism in Alkenes
• Alkenes have many possible structural isomers– Isomers depend not only on the position of the carbons,
but on where the double bond is
Chapter 13 | Slide 23 of 70
A comparison of structural isomerism possibilities for four- and five-carbon alkane and alkene systems.
Chapter 13 | Slide 24 of 70
Cis-Trans Isomerism
• Another kind of isomerism exists in alkenes: _____ _________________________________________– .
C CCH3 CH3
H HC C
CH3
CH3H
H
C CCH3 CH3
H HC C
CH3
CH3H
H
Cis Trans
H H HH
Chapter 13 | Slide 25 of 70
Cis-Trans Isomerism
• Two isomers are possible when groups are attached to the double bond– In a cis isomer, groups are
attached ______________ of the double bond
– In a trans isomer, groups are attached _____________ ______________________ of the double bond.
– Cis-trans isomerism is not possible when ___________ _______________________ _______________________
cis
trans
Chapter 13 | Slide 26 of 70
Draw the cis and trans isomers of 1-chloro-2-pentene.
trans-1-chloro-2-pentene
cis-1-chloro-2-pentene
• Review: How many hydrogens on each carbon?
Chapter 13 | Slide 27 of 70
Learning Check
• Determine whether each of the following substituted alkenes can exist in cis-trans isomeric forms. If they can, draw and name them.– 1-chloropropene
– 2-chloropropene
Chapter 13 | Slide 28 of 70
Learning Check
• Name each, using cis-trans prefixes when needed
C C
BrBr
H H
CH3
C C
CH3H
H
CH3
C C
Cl
H Cl
Chapter 13 | Slide 29 of 70
Cis-Trans Isomers in Nature
• Insects emit tiny quantities of pheromones, which are chemicals that send messages
• The silkworm moth attracts other moths by emitting bombykol, which has one cis and one trans double bond.
HOCH2(CH2)7CH2
C C
C C
CH2CH2CH3
HH
H
H
Chapter 13 | Slide 30 of 70
Terpenes---the basis for cholesterol, steroids and many other biologically active compounds
CH2
C
CH3
CHCH2
Chapter 13 | Slide 31 of 70
Chemical Reactions of Alkenes and Alkynes
• The pi () bond is easily ______, which makes double and triple bonds very ________
• Types of alkene reactions:– _________ reactions
• Symmetrical addition reactions (_____ atom is added to each side of the _________ bond)
– Hydrogenation reaction– Halogenation reaction
• Unsymmetrical addition reactions (_________ atoms are added to the carbons in the ___________ bond)
– Hydrohalogenation reaction– Hydration reaction
Chapter 13 | Slide 32 of 70
Addition Reactions
• _________ are _________ to the carbon atoms in the _________ or ________ bond– In the process, the __________ bond becomes a
_________ bond
C CH
HH
H+ HCl C C
H
HH
H
ClH
Chapter 13 | Slide 33 of 70
In an addition reaction, the atoms provided by an incoming molecule are attached to the carbon atoms originally joined by a double bond.
In the process, the double bond becomes a single bond.
Chapter 13 | Slide 34 of 70
Adds __________________ to each carbon atom of a double bond (catalyst: Pt or Ni)
H H
Ni
H–C=C–H + H2
ethene
Hydrogenation
Chapter 13 | Slide 35 of 70
Adding H2 to vegetable oils produces compounds with
higher melting points (ie. can convert a liquid to a solid)
Margarines
Soft margarines
Shortenings (solid)
Products of Hydrogenation
Chapter 13 | Slide 36 of 70
Fatty acids in vegetable oils are omega-6 acids (the first double bond occurs at carbon 6 counting from the methyl group)
A common omega-6 acid is linoleic acid
CH3CH2CH2CH2CH2CH=CHCH2CH=CH(CH2)7COOH
6
linoleic acid, a fatty acid
Unsaturated Fatty Acids
Chapter 13 | Slide 37 of 70
In vegetable oils, the unsaturated fats usually contain cis double bonds.
During hydrogenation, some cis double bonds are converted to trans double bonds (more stable) causing a change in the fatty acid structure
If a label states “partially” or “fully hydrogenated”, the fats contain trans fatty acids.
Trans Fats
Chapter 13 | Slide 38 of 70
In the US, it is estimated that 2-4% of our total Calories is in the form of trans fatty acid.
trans fatty acids behave like saturated fatty acids in the body.
Several studies reported that trans fatty acids raise LDL-cholesterol. Some studies also report that trans fatty acid lower HDL-cholesterol
The trans fatty acids controversy will continue to be debated.
Trans Fats
Chapter 13 | Slide 39 of 70
Inuit people of Alaska have a high fat diet and high
blood cholesterol levels, but a very low occurrence
of atherosclerosis and heart attacks.
Fat in the Intuit diet was primarily from fish such as
salmon, tuna and herring rather than from land
animals (as in the American diet).
Fats and Atherosclerosis
Chapter 13 | Slide 40 of 70
Fatty acids in the fish oils are mostly the omega-3 type (first double bond occurs at the third carbon counting from the methyl group).
linolenic acid 18 carbon atoms
CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH
eicosapentaenoic acid (EPA) 20 carbon atoms
CH3CH2(CH=CHCH2)5(CH2)2COOH
Omega-3 Fatty acids
Chapter 13 | Slide 41 of 70
Plaques of cholesterol adhere to the walls of the blood vessels
Blood pressure rises as blood squeezes through smaller blood
vessels
Blood clots may form
Omega-3 fatty acids decrease the “sticking” of blood platelets
(fewer blood clots)
Omega-3 fatty acids can increase bleeding time
Atherosclerosis
Chapter 13 | Slide 42 of 70
What is the product of adding H2 (Ni catalyst) to 1-butene?
Learning Check
Chapter 13 | Slide 43 of 70
____________ also add to the carbons in a double or triple bond
H2CCH2 + Cl2
CH3C=CCH2CH3 + 2Br2
Halogenation
Chapter 13 | Slide 44 of 70
Using Bromination to Test for Double Bonds
• Bromine in water has a reddish brown color• If another compound with a double bond reacts with the bromine,
______________________– The reddish color persists ______________________________
___________________________________________________
Chapter 13 | Slide 45 of 70
Write the product of the following addition reactions:
CH3CH=CHCH3 + H2
Learning Check
Chapter 13 | Slide 46 of 70
Hydrohalogenation
• A _________________ is incorporated into the carbons involved in a multiple bond– The _____________ adds to one carbon– The ______________ adds to the other carbon
• Markovnikov’s rule:– .
H3C CH CH2+ H X
Chapter 13 | Slide 48 of 70
Hydration
• A ______________ is incorporated into the carbons involved in a multiple bond– The ___________ adds to one carbon– The ___________ adds to the other carbon
• .• .
H3C CH CH2+ H OH
Chapter 13 | Slide 49 of 70
Learning Check
• Write the products of each reaction
• CH3-CH=CH2 + Cl2
• CH3-CH=CH-CH3 + H2O
• Cyclopentene + H2
Chapter 13 | Slide 50 of 70
Addition Reactions: Polymers
• Polymers are large molecules built up by repetitive bonding of many smaller molecules called ____________________.
• May have thousands of monomer units in one polymer molecule.
• The monomers are __________
C CH
HH
HRadical Catalyst C
CC
CC
CC
CC
C
HH
HH HH HH HH HH
HH HH HH HH
Chapter 13 | Slide 54 of 70
Aromatic Compounds
Aromatic compounds contain _____________.
Benzene has: • .
• .
• Have many properties similar to alkanes
HH
H
H
H
H
H
H
H
H
H
H
Chapter 13 | Slide 55 of 70
Structure of Benzene: Resonance
• Two resonance structures.• Neither resonance form is correct by itself.• The true structure is a combination.
– .
– .
Chapter 13 | Slide 56 of 70
Benzene Structure
The structure for benzene is also written as one
formula with a circle within the ring to represented the
alternating double bonds.
• The circle shows:
Benzene
structure
Chapter 13 | Slide 57 of 70
Aromatic Compounds in Nature and Health
Many aromatic compounds are common in nature and in medicine.
Aspirin Vanillin
Ibuprofen
COH
O
O
C O CH3
CH
O
OCH3
OH
CH
CH3
COH
O
CH2
CH3
CHH3C
Chapter 13 | Slide 58 of 70
Naming Aromatic Compounds
Aromatic compounds are named,• With ________________ as the parent chain. • Side chains are named:
ClCH3
Chapter 13 | Slide 59 of 70
Naming Aromatic Compounds
When two groups are attached to benzene, the ring is numbered to give _________________ _____________________________________.
(para-chloromethylbenzene)(meta-dichlorobenzene)(ortho-dimethylbenzene)
1,2-dimethylbenzene 1,3-dichlorobenzene 1-chloro-4-methylbenzene
Cl
CH3
Cl
Cl
CH3
CH3
Chapter 13 | Slide 60 of 70
Naming Aromatic Compounds
• Disubstituted benzenes are named using prefixes:– .– .– .
Chapter 13 | Slide 61 of 70
Naming Aromatic Compounds
• ortho- (o)• meta- (m)• para- (p)
Br
Br
Br
Br
Br
Br
Chapter 13 | Slide 62 of 70
Naming Aromatic Compounds
• Some aromatic compounds have common names.
OH
NH2
Chapter 13 | Slide 63 of 70
Some Common Names
Some substituted benzenes use common names.
toluene 3-chlorotoluene phenol
(Methylbenzene) (meta-chloromethylbenzene) (hydroxybenzene) Toluene meta-chlorotoluene phenol
OH
Cl
CH3CH3
Chapter 13 | Slide 64 of 70
Learning Check
Select the correct name for each structure:
1) chlorocyclohexane2) chlorobenzene3) 1-chlorobenzene
1) 1,2-dimethylbenzene2) 1,4-dimethylbenzene3) 1,3-dimethylbenzene
CH3
CH3
Cl
Chapter 13 | Slide 65 of 70
Learning Check
Write the structural formulas for each of the following:
A. 1,3-dichlorobenzene
B. 2-chlorotoluene
Chapter 13 | Slide 66 of 70
Naming Aromatic Compounds
• Tri- or higher-substituted benzenes. • Number ________________________________• Use ____________________________________.• Name substituents listed __________________. • If any “common named” monosubstituted parent is used
the principle substituent is on ____________
Br
Chapter 13 | Slide 68 of 70
Chemical Reactions of Aromatic Hydrocarbons
• Aromatic compounds can undergo substitution reactions
– Alkylation • .
– Halogenation • .
– Nitration • .
– Sulfonation • .
Chapter 13 | Slide 69 of 70
Learning Check
• Write the reaction for the bromination of benzene, including the catalyst.