Organic Chemistry

Chapter 22

Structure Determines Properties• Organic compounds all contain carbon

– CO, CO2 , carbonates and carbides are inorganic– Other common elements are H, O, N, (P, S)

• Carbon has versatile bonding patterns – Chains, rings, multiple bonds– Chain length nearly limitless

• Carbon compounds generally covalent – Molecular; Gases, liquids or low melting solids;

Varying solubilities; Nonconductive in liquid

• C - C bonds unreactive (very stable)

Carbon Bonding

• Carbon can bond to other carbon atoms in an almost infinite chain

• Bond to a maximum of four other atoms– Carbon or other elements– Carbon with 4 single covalent bonds = tetrahedral– Carbon with 2 single & 1 double covalent bond =

trigonal planar– Carbon with 1 single & 1 triple covalent bond =

linear

Hydrocarbons• Hydrocarbons contain only C & H

– Aliphatic or aromatic

• Aliphatic hydrocarbons– Saturated or unsaturated aliphatics

• Saturated = alkanes, unsaturated = alkenes or alkynes• Unsaturated have double or triple bonds

– May be chains or rings• Ring molecules have two less H than chain so that ends

can join

– Chains may be straight or branched

Alkanes• a.k.a paraffins• Aliphatic• General formula CnH2n+2 for chains• Very unreactive• Come in chains or/and rings

– CH3 groups at ends of chains, CH2 groups in the middle

• Saturated• Branched or Straight-Chain

– Straight-chain = normal– Condensed formula has CH3 on each end and CH2 in middle

Condensed Structural Formulas• attached atoms listed in order

– central atom with attached atoms

• follow normal bonding patterns– use to determine position of multiple bonds

• () used to indicate more than 1 identical group attached to same previous central atom– unless () group listed first in which case

attached to next central atom

Structural Isomers• Isomers are molecules with the same

molecular formula but different arrangements of the atoms– Different chemical and physical properties

• Structural isomers are isomers in which the atoms are attached differently– Different bonding pattern– Different properties– a.k.a constitutional isomers

Naming• each name consist of 3 parts

¶ prefix • indicates position, number and type of branches • indicates position, number and type of each functional

group

parent• indicates the length of the longest carbon chain or ring

suffix• indicates the type of hydrocarbon

– ane, ene, yne

• certain functional groups

Naming Alkanes

• The first 4 alkanes are methane (C1), ethane (C2), propane (C3), butane (C4)

• After that the names come from adding Greek prefix to –ane

dec10

non9

oct8

hept7

hex6

pent5

PrefixNumber of Carbons

Naming Alkanes Find the longest, continuous carbon chain Number the chain from end closest to a branch

– if first branches equal distance use next in Name branches as alkyl groups

– Branch name related to number of C– End in -yl– locate each branch by preceding its name with the

carbon number on the chain List branches alphabetically

– do not count n-, sec-, t-, count iso Use prefix if more than one of same group present

– di, tri, tetra, penta, hexa– do not count in alphabetizing

Petroleum• Formed when ocean microorganisms died 500

million year ago, were buried, and subjected to large pressures

• A dark, thick liquid composed mainly of hydrocarbons

• Natural gas normally found with petroleum deposits– Mostly methane with some ethane, propane and butane

• Petroleum separated into various fractions by distillation– Separation based on boiling point

Alkenes

• Aliphatic, unsaturated• Formula of chain alkenes - subtract 2 H from

alkane formula for each double bond• C=C double bonds• Trigonal shape around C

– Flat• No rotation

– Cis - trans isomerism• Much more reactive than alkanes• Polyunsaturated = many double bonds

Naming Alkenes

• change suffix on main name from -ane to -ene• number from end closest to double bond• number in front of main name indicates first carbon of

double bond

Naming Alkynes• change suffix on main name from -ane to -yne• number from end closest to triple bond• number in front of main name indicates first carbon of

triple bond

Alkynes• Also known as acetylenes

• Aliphatic, unsaturated

• Formula of chain alkynes - subtract 4 H from alkane for each triple bond

• CC triple bond

• Linear shape

• No rotation

• More reactive than alkenes

Aromatics• Contain 1 or more 6 C unsaturated rings

– Benzene rings

• Chemical reactions different than alkenes– Burn sooty instead of clean– Undergo substitution instead of addition

• Benzene– Liquid, BP = 80°C – All C-C bond lengths and bond angles identical

• 120°• Bond lengths between C-C and C=C

– Planar molecule– Resonance hybrid

CH

CHCH

CH

CHCH

CH

CHCH

CH

CHCH

Naming Benzene Derivatives• main name either benzene or one of the common derivatives• ring numbered from position of main groupor• 2 = ortho (o), 3 = meta (m), 4 = para (p)

p-Cresolm-Toluidineo-XyleneAnisoleAnilinePhenol

AcetophenoneBenzaldehydeBenzoicAcid

StyreneCumeneToluene

C CCH3 CH(CH3)2 CH CH2O

OHO

H

OH NH2

CO

CH3

OCH3 CH3

CH3

CH3

NH2

CH3

OH

Functional Groups• In many organic compounds, C-to-H bonds are replaced by bonds to other atoms

– C-Halogen, C-to-O, C-to-N, occasionally (C-to-S)• These compounds are generally considered hydrocarbon derivatives

– Basically hydrocarbons with a few substitutions• These substituted bonds are more reactive than C-H bonds• Therefore, when molecules with the substituted bonds react, the reaction site is

generally at the substituted bonds• These substituted atoms or groups of atoms are called functional groups, and

they generally determine the chemical reactions an organic molecule will undergo– And also have influences on intermolecular attractions and therefore physical

properties

Alcohols• Have an –OH group in place of a H

• Form H-bonds

– To alcohol molecules and water

• Solubility in water decreases as length of carbon chain increases

• Common reactions include substitution for OH, elimination, oxidation

Naming Alcohols• Select the longest chain of carbon atoms containing the –OH

group

• Number the chain from the end closest to the –OH group

• Determine the parent name from the number of C in the chain, replace the final -e with -ol

• Name alkyl branches as usual

Classifying Carbons• Carbons in an organic molecule are classified based on the

number of other carbons they are attached to

• Primary Carbon, 1°, = carbon attached to one other carbon

• Secondary Carbon, 2°, = carbon attached to 2 other carbons

• Tertiary Carbon, 3°, = carbon attached to 3 other carbons

• Quaternary Carbon, 4°, = carbon attached to 4 other carbons

– Very unreactive

• Hydrogens are classified based on carbon they are attached to– The hydrogens on a 1° carbon are called 1° hydrogens

Classifying Alcohols• alcohols are classified based on the carbon they are

attached to

• Primary Alcohol, 1°, = OH group on 1° C

• Secondary Alcohol, 2°, = OH group on 2° C

• Tertiary Alcohol, 3°, = OH group on 3° C

CH3 CH2

CH

CH3

CH3

CH2

CH2

CH

CH3

CH3

OH

CH3 CH

CH

CH3

CH3

OH

CH3 CH2

C CH3

CH3

OH

1° alcohol 2° alcohol 3° alcohol

1° 2° 3°1°

Aldehydes and Ketones

• Both contain C=O, carbonyl group• In ketones, the carbonyl group is attached to

2 carbon atoms– In middle of a chain or ring

• In aldehydes, the carbonyl group is attached to a carbon and a hydrogen– Or 2 H in the case of formaldehyde– Must be on the end of a chain

Ketones

• Often used as polar solvent when presence of OH cause problems

• Acetone – R1 = R2 = CH3

– Nail polish remover, paint solvent• MEK = methyl ethyl ketone – R1= CH3, R2 = CH2CH3

– Paint solvent, gasoline additive

Aldehydes• Often strong odors, Used as fragrances and food additives• Formaldehyde – R1 = R2 = H

Gas, when dissolved in water = formalin Suspected carcinogen Used in the production of foams and adhesives

• Acetaldehyde – R1 = H, R2= CH3

R1 C R2

O

Naming Aldehydes• Select the longest chain of carbon atoms containing the aldehyde group

• Number the chain calling the carbonyl C position 1

• Determine the parent name from the number of C in the chain, replace the final -e with -al

• Name alkyl branches as usual

Naming Ketones• Select the longest chain of carbon atoms containing the carbonyl group

• Number the chain from the end closest to the carbonyl group

• Determine the parent name from the number of C in the chain, replace the final -e with -one

• Name alkyl branches as usual

Carboxylic Acids

• Have carboxyl group, R1-COOH• Always on end of chain• Acid functional group

– Weak acid

• Made by oxidation of 1° alcohols – under stronger conditions

• Formic Acid, R1 = H– Bee and ant stings

• Acetic Acid, R1 = CH3

– vinegar

R1 C OH

O

Esters• Replace acid H of carboxy group with R group,

R1-COOR2

• Sweet, fruity odors

• Made by reacting carboxylic acid with an alcoholR1-COOH + R2-OH R1-COOR2 + H2O

– Not like neutralization, alcohol not a base!

R1 C

O

O R2

Naming Carboxylic Acids• Select the longest chain of carbon atoms containing the

carboxy group

• Number the chain calling the carboxy C position 1

• Determine the parent name from the number of C in the chain, replace the final -e with –oic acid

• Name alkyl branches as usual

Naming Esters• Select the longest chain of carbon atoms containing the ester group

• Name R2 as alkyl group

• Name R1 and carboxy C like acid except change the –ic ending to -ate

• Put the pieces together, alkyl group first

Polymers• Generally organic molecules

• Very large, molar masses 10,000+

• Chain-like molecules made by linking together small molecules called monomers– Monomer units usually indicated in name with

the prefix “poly-”– polyethylene, polypropylene, polystyrene

Linking Monomers• Addition Polymerization = monomers

linked by each molecule attaching to chain by a synthesis type reaction

• Condensation Polymerization = monomers linked when a reaction occurs that splits out a small molecule, like water

• Homopolymers all monomer units alike

• Copolymers have multiple monomer units