organic chemistry ch. 11 and 12. what is organic chemistry? what does organic mean to you? the name...
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Organic ChemistryOrganic ChemistryCh. 11 and 12Ch. 11 and 12
What is Organic chemistry?What is Organic chemistry?• What does organic mean to you?• The name organic was given to molecules
found in living organisms• Now, organic chemistry refers to the chemistry
of carbon compounds– Carbon is important to life because of its ability to
form an endless number of molecules• CH4 – methane gas• Proteins• Cotton, wool, silk• CH3CH2OH - Ethanol
Organic CompoundsOrganic Compounds
Typically, organic compounds
Contain carbon.
Have covalent bonds.
Have low melting points.
Have low boiling points.
Are flammable.
Are soluble in nonpolar solvents..
Bonding in Organic CompoundsBonding in Organic Compounds• Carbon has 4 valence electrons (lone
electrons)
C • This means there are four places for it to
bound to other atoms in order for carbon to achieve an octet
C
•
• •
•
•••
•1
3
24
Bonding with HydrogenBonding with Hydrogen Carbon has 4 lone electrons; hydrogen has 1.Carbon has 4 lone electrons; hydrogen has 1.
••
•• C C • • H H •• ••
To achieve an octet, carbon forms four bonds. To achieve an octet, carbon forms four bonds. HH H H
• • • • ||H H C C H H H H——CC——HH CH CH4 4 , , methanemethane
• •• • || HH H H
Tetrahedral Nature of CarbonTetrahedral Nature of Carbon
• When carbon forms four bonds to other atoms, the bonds are situated 109.5o apart from each other.
• This arrangement is a
tetrahedral arrangement.
Organic MoleculesOrganic Molecules• In organic molecules, valence electrons form
covalent bonds between carbon atoms• Molecules consisting of only carbon and
hydrogen are call hydrocarbons H H H H
• • • • | |
H C C H H—C—C—H Ethane,CH3CH3
• • • • | | H H H H
Other ElementsOther Elements
• Carbon in organic compounds also commonly forms covalent bonds with N, O, S, and halogens (Cl, Br)
Learning CheckLearning Check
• Complete the structure of the organic molecule by adding the correct number of hydrogen atoms.
C—C—C
Learning CheckLearning Check• Complete the structure of the organic
molecule by adding the correct number of hydrogen atoms.
H H H | | | H—C—C—C—H | | |
H H H
AlkanesAlkanes• Hydrocarbons that contain only carbon-carbon single bonds
• General formula = CnH2n+2
– n = number of carbons
Uses of AlkanesUses of Alkanes• Small number of carbons (1 – 4
carbons)– gases– Heating fuels – propane, butane
• 5 – 8 carbons– Liquids– Fuels – gasoline, kerosene, diesel,
jet fuel• 18 + carbons
– Waxy solids– Waxes (paraffins), Vaseline
Conformation of AlkanesConformation of Alkanes• Because of the tetrahedral shape of carbon bonds,
carbon bonds are in a zigzag pattern
• Atoms can rotate around a single carbon-carbon bond– Different arrangements that can occur because of this
are called conformations
Expanded and Condensed Expanded and Condensed FormulasFormulas
• Expanded structural formula = all individual bonds (indicated with dashes) and atoms are drawn
• Condensed structural formula =each carbon atom is grouped with its bonded hydrogen atoms. Subscripts are used to indicate number of H’s and bonds are indicated with dashes
• Skeletal Formula= only carbons and bonds(as dashes) are represented- Hydrogens are implied
Expanded and Condensed Expanded and Condensed FormulasFormulas
• Line bond formulas = lines represent carbon-carbon bonds. No individual atom is indicated. Hydrogens and Carbons are implied.
• Molecular Formula= Atoms are represented and subscripts are used to indicate the number of each atom. No bonds are drawn.
• Geometric Formula= Similar to line bond formulas, but used for cyclic compounds.
IUPACIUPAC• International Union of Pure and Applied
Chemistry• Determined protocol for naming organic
compounds• Pentane
– Prefix states number of carbons• Pent - = five carbons
– Suffix shows kind of compound• -ane = alkane, only single carbon bonds
Prefixes (Table 11.2)Prefixes (Table 11.2)
CycloalkanesCycloalkanes• Hydrocarbons do not need to be in a chain, they
can also form circular structures
CycloalkanesCycloalkanes
• Cycloalkanes: • Are rings of carbons that can be drawn as
geometric figures. • Have a general formula of CnH2n or 2 H less than
the alkane. • propane C3H8 cyclopropane C3H6. • butane C4H10 cyclobutane C4H8. • Are named with the prefix cyclo- in front of the
corresponding alkane name.
Table 11.4Table 11.4
Cyclopropane CyclohexaneCyclopentaneCyclobutane
LINE BOND FORMULAS FOR SOME CYCLOALKANES
C3H6 C4H8 C5H10 C6H12
Naming AlkanesNaming Alkanes• Molecular formulas do not tell us the structure
– constitutional isomers
• Carbon compounds can be continuous-chain or branched-chained
SubstituentsSubstituents
• Substituents are groups of atoms that replace a hydrogen on a carbon chain– Blue flashcards! *need to know!!*
• If the substituent is a hydrocarbon, it is called an alkyl group– The alkyl group is named by replacing the –
ane with -yl
Some of these included in Table 11.5
Steps for naming alkanesSteps for naming alkanes1. Name the longest continuous chain of
carbons as the main chain2. Number the carbon atoms in the main
chain starting on the end nearest a substituent
-Where there are 2 or more substituents, the main chain should be numbered to give the lowest possible number set
Naming Alkanes Cont. Naming Alkanes Cont. 3. Give the location and name of each alkyl
group in front of the name of the main chain- use prefixes (di-, tri-) if a group appears more than once
4. List the substituents in alphabetical order
NamingNaming
• 1. Name Longest Chain First= hexane
• 2. Number Carbons from the end with the nearest substituent.
CH3-CH-CH2-CH-CH2-CH3
CH3 CH2CH3
1 2 3 4 5 6 CH3-CH-CH2-CH-CH2-CH3
CH3 CH2CH3
3. Give the location and name of each alkyl group in front of the name of the main chain2-methyl-4-ethylhexane
4. List substituents in alphabetical order. 4-ethyl-2-methylhexane
NamingNaming
• 1. Name Longest Chain First= heptane
• 2. Number Carbons from the end with the nearest substituent.
1 2 3 4 5 CH3-CH-CH2-CH2-CH-CH3
CH3 6 CH2CH3
7
CH3-CH-CH2-CH2-CH-CH3
CH3 CH2CH3
3. Give the location and name of each alkyl group in front of the name of the main chain2,5-dimethylheptane
4. List substituents in alphabetical order. Fine as is!
Try a Few!Try a Few!
• On board exercise!
Drawing Structural FormulasDrawing Structural Formulas
Step 1 – Draw the main chain of carbon atoms
Step 2 – Draw the substituents on the main chain in the positions indicated by the location numbers
Step 3 – Fill in the correct number of hydrogen atoms to give four bonds to each carbon atom
Draw 2,3-dimethylpentaneDraw 2,3-dimethylpentane
1. Draw Main Chain of Carbon atoms
C-C-C-C-CC-C-C-C-C
2. Draw the substituents on the main chain in the positions indicated by the location numbers
C-C-C-C-C
C C
3. Fill in the correct number of hydrogen atoms to give four bonds to each carbon atom
CH3-CH-CH-CH2-CH3
CH3 CH3
Try a few!Try a few!
• 2,3,5-trimethylhexane
• 3-ethylpentane
• 4-isopropyloctane
IsomersIsomers
• Molecules with the same molecular formula but different structural formula
• Example: C5H12
CH3-CH2-CH2-CH2-CH3
CH3-CH-CH2-CH3
CH3
Constitutional IsomersConstitutional Isomers
• Most organic compounds have structural isomers and their number increases as the number of atoms increases
Physical Properties of Constitutional Isomers
Different structural arrangement can result in very different physical properties
Drawing IsomersDrawing Isomers
• Step 1 – Draw the longest continuous chain
• Step 2 – Remove one carbon from the chain and attach it as a methyl group in as many locations as possible
• Step 3 – Remove another carbon atom from the main chain and attach as another alkyl group
Try SomeTry Some
• Draw isomers for C4H10
– Practice Naming!!
HaloalkanesHaloalkanes• An alkane in which halogen atoms replace
one or more hydrogens• Used as solvents and anesthetics• CFC’s (chlorofluorocarbons) were used a
propellants in aerosols– React with ozone in the upper atmosphere– Resulted in ozone depletionover the Antarctic
Naming HaloalkanesNaming Haloalkanes
• IUPAC names for halogen substituents are:
• Fluorine = fluoro-• Chlorine = chloro-• Bromine = bromo-• Iodine = iodo-
• The halo-substituents are numbered and arranged alphabetically, like we did before
Other substituents
• Use the same naming rules– Number position on the parent chain– Put in alphabetical order
CH3-CH-CH2-CH3
Cl
Naming Cycloalkanes
A cycloalkane with: One substitutuent is named by placing the
name of the substituent in front of the cycloalkane name.
Two or more substitutuents is named by numbering the ring in the direction that gives the lower numbers to the substituents.
Cycloalkanes with Side Groups
CH3
CH3
CH3
CH3
CH3
CH3
methylcyclopentane
1,2-dimethylcyclopentane
1,2,4-trimethylcyclohexane
Try Some!Try Some!
• On Board Exercise
Worksheet 1Worksheet 1• You can now complete worksheet 1.
Alkanes are typically not very reactive due to strong C-C single bonds.
The most typical reaction is combustion, where an alkane reacts with oxygen to produce carbon dioxide, water, and energy.
alkane + O2 CO2 + H2O + energy
Chemical Properties of Alkanes
Combustion
A fuel such as propane reacts with oxygen and burns, producing CO2 and H2O.
Propane is burned to obtain energy and heat for cooking or warming a room.
C3H8 + 5O2 3CO2 + 4H2O
Incomplete combustionIncomplete combustion
• It is dangerous to burn fuels in a closed room
• With limited amounts of oxygen, incomplete combustion occurs– This produced carbon monoxide, which is a toxic
gas
2CH4(g) + 3O2(g) 2CO(g) + 4H2O(g) + heat
Balancing Combustion Balancing Combustion ReactionsReactions
• Use the CHO method- Balance Carbons first, then hydrogens, then oxygens
• C3H8 + O2 CO2 + H2O
• C3H8 + O2 3 CO2 + H2O
• C3H8 + O2 3 CO2 + 4 H2O
• C3H8 + 5 O2 3 CO2 + 4 H2O
Balancing Combustion Balancing Combustion ReactionsReactions
• You may have to use fractions to start!
• CH4(g) + O2(g) CO(g) + H2O(g)
• CH4(g) + O2(g) CO(g) + 2H2O(g)
• CH4(g) + 3/2 O2(g) CO(g) + 2H2O(g)
• 2[CH4(g) + 3/2 O2(g) CO(g) +2 H2O(g)]
• 2CH4(g) + 3O2(g) 2CO(g) + 4H2O(g)
Classifying Carbon AtomsClassifying Carbon Atoms
• Primary Carbons (1o)- Bonded to only one other carbon atom
• Secondary Carbons (2o)- Bonded to two other carbon atoms
• Tertiary Carbons (3o)- Bonded to three other carbons
Functional GroupsFunctional Groups• Millions of compounds possible• However, certain structures behave in
similar manners• These are called functional groups• For now: • Alkanes
– Saturated Hydrocarbons
• Alkenes, Alkynes, Aromatics– Unsaturated Hydrocarbons
Background: Double BondsBackground: Double Bonds
• Two nonmetal atoms can share more than one set of electrons
• Sharing four electrons = double bond
H H
C C
H H••• ••
•••• ••
•
Background: Triple BondsBackground: Triple Bonds
• Two nonmetals can also form triple bonds = sharing 6 electrons
Alkenes, Alkynes and AromaticsAlkenes, Alkynes and Aromatics• Alkanes contain only single bonds
• Alkenes contain one or more double bonds
• Alkynes contain one or more triple bonds
• Aromatic ring (benzene) is 6 carbons cyclized with alternating double bonds
Unsaturated hydrocarbons:
Have fewer hydrogen atoms attached to the carbon chain than alkanes.
Are alkenes with double bonds or alkynes with triple bonds.
Ch. 12-Unsaturated Hydrocarbons
AlkenesAlkenes• Contain at least one
double bonds• Important in
manufacturing and in human and plant functioning– Hormones– Ripening fruit– Ethene used to make
polymers
AlkynesAlkynes
• Contain at least one triple bond
• Not found in nature often
• Acetylene– used in welding torches
+
In the IUPAC system, the –ane ending of the corresponding alkane is changed to –ene for alkenes and to –yne for alkynes.
Naming Alkenes and Alkynes
When the carbon chain has 4 or more C atoms, the chain is numbered to give the lowest number to the double or triple bond.
1
CH2=CH—CH2—CH3 1-butene 2
CH3—CH=CH—CH2—CH3 2-pentene 3
CH3—CH2—CC—CH2—CH3 3 -hexyne
Naming Alkenes and Alkynes
More NamingMore Naming
• If you have more than 1 double or triple bond:– Name them as dienes or diynes
• CH2=CH—CH2—CH2=CH3 1, 4 - pentadiene
1 2 3 4 5
• CHC—CH2—CC—CH2—CH3 ????
More NamingMore Naming• If you have more than 1 double or triple bond:
– Name them as dienes or diynes
• CH2=CH—CH2—CH2=CH3 1, 4 - pentadiene
1 2 3 4 5
• CHC—CH2—CC—CH2—CH3
1, 4 - heptadiyne
Alkenes and Alkynes with Alkenes and Alkynes with SubstituentsSubstituents
• 1. Name the longest carbon chain that contains the double or triple bond
• 2. Number the chain starting at the end nearest the double or triple bond.
4-methyl-1-pentene
Try One!Try One!
Naming Cyclic Alkenes and Naming Cyclic Alkenes and AlkynesAlkynes
• Use –ene instead of -ane
• The double bond of a cycloalkene is understood to be between Carbon 1 and Carbon 2. Number from there to get the lowest possible number set.
Practice!Practice!
• On Board Exercise
Cis-Trans IsomersCis-Trans IsomersDouble Bonds do not rotate freely!Introducing a new type of isomer!
Cis-Trans IsomersCis-Trans Isomers Two isomers are possible
when groups are attached to the double bond.
In a cis isomer, groups are attached on the same side of the double bond. symmetrical
In the trans isomer, the groups are attached on opposite sides. unsymmetrical
Naming Cis-Trans Isomers
The prefixes cis or trans are placed in front of the alkene name when there are cis-trans isomers.
cis-1,2-dibromoethene trans-1,2-dibromoethene
C C
Br H
BrH
C C
Br Br
H H
Worksheet 2Worksheet 2• You can now complete worksheet 2.
Addition ReactionsAddition Reactions
Double and triple bonds are weaker than single bonds More reactive
In the addition reaction, reactants are added to the carbon atoms in the double or triple bond.
Addition ReactionsAddition Reactions
• H2C=CH2 + A—B H2C—CH2
A B
HydrogenationHydrogenation In hydrogenation, hydrogen atoms add to the
carbon atoms of a double bond or triple bond. A catalyst such as Pt or Ni is used to speed up
the reaction.
HC CH + 2H2Ni
HC CH
H H
H H
H2C CH2
H HPt
H2H2C CH2 +
Hydrogenation of OilsHydrogenation of Oils
When hydrogen adds to the double bonds in vegetable oils, the products are solids at room temperature.
HalogenationHalogenation
• In halogenation, halogen atoms add to the carbon atoms of a double bond or triple bond.
+ HC C CH3 2Cl2 C C
Cl Cl
Cl Cl
CH3H
H2C CH2
Br Br
Br2H2C CH2 +
Testing for Double and Triple Testing for Double and Triple BondsBonds
• When bromine (Br2) is added to an alkane, the red color of bromine persists.
• When bromine (Br2) is added to an alkene or alkyne, the red color of bromine disappears immediately.
HydrohalogenationHydrohalogenation
• In hydrohalogenation, the atoms of a hydrogen halide add to the carbon atoms of a double bond or triple bond.
CH3 CH CH CH3
H Cl
+ HClCH3 CH CH CH3
H
Br
+ HBr
Markovnikov’s RuleMarkovnikov’s Rule
• When an unsymmetrical alkene undergoes hydrohalogenation, the H in HX adds to the carbon in the double bond that has the greater number of H.
CH3 CH CH2
Cl H
CH3 CH CH2 + HCl
CH3 CH CH2
H Cl
Does not form
C with the most H
Product that forms
Hydration Adds WaterHydration Adds Water
• In hydration, H and OH from water add to the carbon atoms of a double bond or triple bond to form alcohols (OH).
• The reaction is catalyzed by acid H+.
+ HOHH
OH
CH3 CH CH2 + HOH
CH3 CH CH2
OH H
H+
H+
Worksheet 3Worksheet 3• You can now complete worksheet 3.
Aromatic CompoundsAromatic CompoundsBenzene is An aromatic compound.
A ring of 6 C atoms and 6 H atoms. Alternating single and double bonds Aromatic compounds often have fragrant
odors
Aromatic Compounds in Nature and Medicine
A benzene with a single substituent is often named as a benzene derivative.
Methylbenzene Chlorobenzene A benzene ring as a substituent is called a phenyl-
group
Naming Aromatic Compounds
ClCH3
Some substituted benzene rings have common names that have been in use for many years.
Also, know naphthalene (2 fused rings)
Some Common Names
CH3 NH2 OH
Toluene Aniline Phenol(Methylbenzene) (Benzenamine) (Hydroxybenzene)
A benzene ring with two or more substituents is numbered to give the lowest numbers to the side groups.
Common names use the prefixes ortho- (1,2-), meta- (1,3-) and para- (1,4-).
Naming Aromatic Compounds
Br
Br
Cl
Cl
CH3
Cl
1,2-dimethylbenzene 1,3-dichlorobenzene 4-chloromethylbenzene(o-dibromobenzene) (m-dichlorobenzene) (p-chlorotoluene)