Organic Chemistry CH. 25. Definitions Organic means “based on carbon” Hydrogen, oxygen, and...

Organic ChemistryCH. 25

Definitions• Organic means “based on carbon” • Hydrogen, oxygen, and other

elements are sometimes present• Inorganic means all those

compounds without carbon• Exceptions: Diamond, graphite,

carbon dioxide

What’s So Special About Carbon?

• It can form 4 covalent bonds• With other carbon atoms• With other elements• Forms long chains (straight or

branched)• Rings and hoops

Types of Carbon Atoms

• Primary carbon (1o)– a carbon bonded to one other carbon

• Secondary carbon (2o)– a carbon bonded to two other carbons

• Tertiary carbon (3o)– a carbon bonded to three other carbons

C

C

C

C

H

H

H

C C

H

HC

C

C

H

C

C

C

C

H

H

H

C C

H

HC

C

C

H

C

C

C

C

H

H

H

C C

H

HC

C

C

H

C

C

C

C

H

H

H

C C

H

HC

C

C

H

Some organic chemicals

DNA

Essential oils

Medicines•Active Pharmaceutical Ingredients•Excipients

Materials

Fuels

Pigments

Hydrocarbons

• Compounds which contain only carbon and hydrogen

• Obtained from petroleum distillation• Fuels, solvents, lubricants, waxes,

paving materials• Starting materials for countless other

products

Hydrocarbons- Types

• Aliphatic Long chains (can be branched)

• Alicyclic Rings or hoops

Aliphatic Hydrocarbons

• 2 Types

• Saturated (only single bonded carbons)

• Unsaturated (can contain double or triple bonded carbons)

Saturated Hydrocarbons:Alkanes

• All end in –ane• Only single bonds• Generic formula CnH(2n+2) • Known as a homologous series (add CH2

unit each time)– Methane CH4 (Natural Gas)– Propane C3H8 (common fuel gas)– Butane C4H10 (common fuel gas)– Gasoline (A mixture of liquid hydrocarbons

from heptane C7H16 to Decane C10H22

Alkanes

The First 10 “Normal” AlkanesName Formula M.P. B.P. # Structural Isomers

• Methane CH4 -183 -162 1

• Ethane C2H6 -172 -89 1

• Propane C3H8 -187 -42 1

• Butane C4H10 -138 0 2

• Pentane C5H12 -130 36 3

• Hexane C6H14 -95 68 5

• Heptane C7H16 -91 98 9

• Octane C8H18 -57 126 18

• Nonane C9H20 -54 151 35

• Decane C10H22 -30 174 75

C1 - C4 are Gases at Room Temperature

C5 - C16 are Liquids at Room Temperature

Prefixes for # of Carbons

1 Meth 6 Hex

2 Eth 7 Hept

3 Prop 8 Oct

4 But 9 Non

5 Pent 10 Dec

IUPAC Rules for Naming Branched Alkanes

– Find and name the parent chain in the hydrocarbon - this forms the root of the hydrocarbon name

– Number the carbon atoms in the parent chain starting at the end closest to the branching

– Name 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 alphabetically

– Finally, use prefixes to indicate multiple branches

Branched- Chains

• Designate the location (number of the carbon on the parent chain) for each attached group

1 2 3 4 5

2-methyl

Some Simple Alkanes

• 2-methylpentane

• 3-ethylhexane

• 2,2-dimethylbutane

• 2,3-dimethylbutane

Example 1: 2,2-dimethylpentane

• The parent chain is indicated by the ROOT of the name - “pentane”. This means there are 5 carbons in the parent chain.

CH3

CH2CH2

CH2CH3

• “dimethyl” tells us that there are TWO methyl branches on the parent chain. A methyl branch is made of a single carbon atom.

• “2,2-” 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-dimethylheptane• The parent chain is indicated

by the ROOT of the name - “heptane”. This means there are 7 carbons in the parent chain.

CH3

CH2CH2

CH2CH2

CH2CH3

• “2,4-dimethyl” tells us there are TWO methyl branches on the parent chain, at carbons #2 and #4.

• “3-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

CH2CH3

CH3 CH3

Example 3: 2,3,3-trimethyl-4-propyloctane• The parent chain is indicated

by the ROOT of the name - “octane”. This means there are 8 carbons in the parent chain.

• “2,3,3-trimethyl” tells us there are THREE methyl branches - one on carbon #2 and two on carbon #3.

• “4-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-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 alphabetically3,4-dimethyl

43

octane

5

5-ethyl-

Isomers

• Straight chain alkanes: An alkane that has all its carbons connected in a row.• Branched chain alkanes: An alkane that has a branching connection of carbons.

Structural Isomerism

• Structural isomers are molecules with the same chemical formulas but different molecular structures - different “connectivity”.

• They arise because of the many ways to create branched hydrocarbons.

CH3

CH2CH2

CH2CH3

CH3

CH2CH

CH3

CH3

n-pentane, C5H12

2-methlbutane, C5H12

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Isomers• Isomers - organic molecules that have:

– Identical molecular formulas, but– Differing internal arrangement of atoms

•Different isomers are completely different compounds. They have different structures, different physical properties such as melting point and boiling point, and may have different physiological properties.

•Isomers: carbons in butane (C4H10) can be arranged in two ways; four carbons in a row (linear alkane) or a branching (branched alkane). These two structures are two isomers for butane.

Learning Check

• Draw all possible structural isomers of C5H12

Unsaturated HydrocarbonsAlkenes

• 1 Double Bond• Homologous Series remains the same, add

CH2 each time

• Generic formula CnH2n

• Ethene (C2H4) common name ethylene

• Butene (C4H8)

• 2 double bonds are called Dienes• 3 double bonds are called Trienes

Unsaturated HydrocarbonsAlkynes

• Contains a triple bond• Names end in -yne• Generic formula CnH(2n-2)

• Most Familiar example is ethyne• Common name acetylene C2H2

• Welding fuel kept dissolved in acetone

Naming Alkenes and Alkynes

When the carbon chain has 4 or more C atoms, number the chain to give the lowest number to the double or triple bond.

1 2 3 4

CH2=CHCH2CH3 1-butene

CH3CH=CHCH3 2-butene

CH3CCCH3 2-butyne

Alicyclic Hydrocarbons

• 2 types• Saturated rings

– Cyclohexane C6H12

• Aromatic rings– Benzene C6H6

Alkanes - Cycloalkanes• 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!•What is the general formula for a cycloalkane?

CycloalkanesCycloalkanes: An alkane that contains a ring of carbon atoms. Ring sizes from 3 carbons to 30 or higher are known.

Drawing and Naming Cycloalkanes

Cycloalkanes are represented by polygons. A triangle represents cyclopropane, a square represents cyclobutane, a pentagon represents cyclopentane, and so on.

•Line structure: A shorthand way of drawing structures in which atoms aren’t shown; instead a carbon atom is understood to be at each corner and hydrogens are “understood”.

•Step 1: Use the cycloalkane name as the parent chain.•Step 2: Number the substituents starting at the group that has alphabetical priority, and proceed around the ring in the direction that gives the second substituent the lower possible number.

Additional Rules for Naming Cyclics

Cycloalkanes with Side Groups

CH3

CH3

CH3

CH3

CH3

CH3

methylcyclopentane

1,2-dimethylcyclopentane

1,2,4-trimethylcyclohexane

Learning Check

Write the IUPAC name for each of the following unsaturated compounds:

A.CH3CH2CCCH3

CH3

B. CH3C=CHCH3 C.

CH3

Learning CheckCH3

CH3

CH3

CH3

CH3

Name those alkenes...

CH

CH

CH3 CH CH3

CH3

CH

CH

CH2

CH2

CH2

Br

cis-4-methyl-2-pentene2-methyl-2-hexene

cyclopentene

cis-3-heptene

trans-2-bromo-3-methyl-2-pentene

Cis and Trans Isomers

Double bond is fixed Cis/trans Isomers are possible

CH3 CH3 CH3

CH = CH CH = CH

cis trans CH3

Cis- and Trans- terminologyIf alkenes have two different substituents at each end

of the C=C then they can exist as stereoisomers because there is restricted rotation of the double bond.

• In cis isomers, two methyl groups are close together on the same side of the double bond.

• In trans isomer, two methyl groups are far apart on opposite side of the double bond.

• Both cis and trans isomers have the same formula and connections between the atoms but have different three dimensional structures because the way the groups are attached to the carbons.

• Cis-trans isomerism occurs in an alkene whenever each double bond carbon is bonded to two different substituent groups. Cis-trans isomerism is not possible if one of the double bond carbons is attached to two identical groups.

Name These

C CCH3

H

CH3

CH2CH3

C CCl

H

CH2

Cl

CH3

Aromatic 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

• Experimental evidence suggest that all six carbon-carbon bonds in benzene are identical.

• The properties, including the above one, of benzene can only be explained by assuming that the actual structure of benzene is an average of the above two possible equivalent structures-known as resonance.

• Simple aromatic compounds like benzene are non-polar, insoluble in water, volatile, and flammable.

• Unlike alkenes, several aromatic hydrocarbons are toxic. Benzene itself is implicated as a cancer causing chemical.

Aromatic Compounds in Nature and Health

Many aromatic compounds are common in nature and in medicine.

COOH

COOCH3

CHO

OCH3

OH

Aspirin Vanillin

CHCOOH

CH3

CH3CHCH2

CH3

Ibuprofen

Naming Aromatic Compounds

Aromatic compounds are named with benzene as the parent chain. One side group is named in front of the name benzene. - No number is needed for mono-substituted benzene since

all the ring positions are identical.

methylbenzene chlorobenzene (toluene)

CH3 Cl

Naming Aromatic Compounds

When two groups are attached to benzene, the ring is numbered to give the lower numbers to the side groups. The prefixes ortho (1,2), meta (1,3-) and para (1,4-) are also used.

CH3

CH3

Cl

Cl

Cl

CH3

1,2-dimethylbenzene 1,3-dichlorobenzene 1-chloro-4-methylbenzene

(ortho-dimethylbenzene) (meta-dichlorobenzene) (para-chloromethylbenzene)

Some Common Names

Some substituted benzene rings also use a common name. Then naming with additional more side groups uses the ortho-, meta-, para- system.

CH3

Cl

CH3 OH

Toluene meta-chlorotoluene phenol(Methylbenzene) (meta-chloromethylbenzene) (hydroxybenzene)

• Many substituted aromatic compounds have common names in addition to their systematic names.

Learning Check

Select the names for each structure:

a. Chlorocyclohexaneb. Chlorobenzenec. 1-chlorobenzene

a. Meta-xyleneb. Meta-dimethylbenzenec. 1,3-dimethylbenzene

Cl

CH3

CH3

New Attached Groups

• Phenyl

• Benzyl

• Nitro -NO2

2,4,6-trinitrotoluene

Benzyl alcohol

4-phenyl-1-butene

Refer to your chart for order of priority!

Organic Chemistry:

Functional Groups

Origin of organic compounds

• Naturally occurring organic compounds are found in plants, animals, and fossil fuels

• All of these have a plant origin• All of these rely on the “fixing” of C from CO2

• Synthetic organic compounds are derived from fossil fuels or plant material

• Organic reactions often much slower than inorganic reactions–must break strong covalent bond–trying to find new catalysts to use

• Substitution Reactions- an atom (or group of atoms) replaces another atom or group of atoms

Substitution Reactions

• A halogen (shown as “X”) can replace a hydrogen to make a halocarbon:R-H + X2 R-X + HX

• Sunlight is often a sufficient catalyst:

CH4 + Cl2 → CH3Cl + HClUV light

SUBSTITUTIONSATURATED COMPOUNDS ONLY

ONE KIND OF ATOM OR GROUP IS SUBSTITUTED WITH ANOTHER KIND OF ATOM OR GROUP

PRODUCE HALIDES

C4H10 + Cl2 → C4H9Cl + HCl

TRY THESE!C3H8 + I2 → C3H7I + HI

C7H16 + F2 → C7H15F + HF

BE ABLE TO DRAW REACTANTS AND PRODUCTS

BE ABLE TO

NAME

PRODUCTS

Addition Reactions

• The carbon-carbon single bond is not easy to break

• In double bonded alkenes, it is easier to break a bond

• Addition reaction- substance is added at the double or triple bond location, after it is broken

Addition Reactions

• If a halogen is added in an addition reaction, the result is a halocarbon that is disubstituted - middle p. 734

• The addition of bromine is often used as a test for saturation - p.734

• Addition of a hydrogen halide? -called monosubstituted halocarbon

ADDITION RxnsADDING 2 OR MORE ATOMS TO CARBON ATOMS THAT ARE ATTACHED TO OTHER CARBON ATOMS BY DOUBLE OR TRIPLE BONDS.

OCCUR MORE EASILY THAN SUBSTITUTION

HOW HALIDES ARE MADE

ALKENES AND ALKYNES

C6H12 + Cl2 → C6H12Cl2

TRY THESE!!C7H14 + Br2 → C7H14Br2

C3H6 + I2 → C3H6I2

BE ABLE TO DRAW AND

NAME REACTANTS

AND PRODUCTS

POLYMERIZATION

CONDENSATION

• MONOMERS JOIN BY DEHYDRATION (DEHYDRATION SYNTHESIS).

• I.E. POLYESTERS, SILICONES, NYLONS, SOME PLASTICS

ADDITION• OPENING OF

DOUBLE AND TRIPLE BONDS TO JOIN MONOMERS.

• I.E. VINYL PLASTICS LIKE POLYETHELENE AND POLYSTYRENE.

LARGE MOLECULES(POLYMERS) ARE MADE FROM SMALLER MOLECULES CALLED MONOMERS.

CAN

BE

NAT

URA

L O

R SY

NTH

ETIC

PRO

TEIN

S, S

TARC

HES

,RU

BBER

NYL

ON

, PO

LYES

TER,

RU

BBER

D. Polymers • Polymers – large chainlike molecules made from many small molecules called

monomers – Simplest polymer – polyethylene– Polyethylene results from addition polymerization.

D. Polymers • Condensation polymerization – a small

molecule (often water) is released for each addition of a monomer to the polymer chain

• Copolymer – 2 different types of monomers combine to form the chain

– Nylon

Functional Groups• Most organic chemistry involves

substituents–often contain O, N, S, or P–also called “functional groups”-

they are the chemically functional part of the molecule, and are the non-hydrocarbon part

Functional Groups• Functional group - a specific

arrangement of atoms in an organic compound, that is capable of characteristic chemical reactions.–What is the best way to classify

organic compounds? By their functional groups.

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Functional Groups

• A functional group is an atom or a group of atoms with characteristic chemical and physical properties. It is the reactive part of the molecule.

• Most organic compounds have C—C and C—H bonds. However, many organic molecules possess other structural features:

Heteroatoms—atoms other than carbon or hydrogen. Bonds—the most common bonds occur in C—C and C

—O double bonds. These structural features distinguish one organic

molecule from another. They determine a molecule’s geometry, physical properties, and reactivity, and comprise what is called a functional group.

Introduction to Organic Molecules and Functional Groups

74

• Heteroatoms and bonds confer reactivity on a particular molecule.

Heteroatoms have lone pairs and create electron-deficient sites on carbon.

Bonds are easily broken in chemical reactions. A bond makes a molecule a base and a nucleophile.

Don’t think that the C—C and C—H bonds are unimportant. They form the carbon backbone or skeleton to which the functional group is attached.

75

Polar; some sugarsExample: Acetone

Polar, forms H-bonds; some sugarsand amino acids Example: EthanolR OH

R HCO

R RCO

R OHCO

R HN H

R SH

Biologically ImportantFunctional Groups

Thiols

AminesAmino

CarboxylicAcidsCarboxyl

Ketones

AldehydesCarbonyl

AlcoholsHydroxylCompoundStructureGroup Significance

Polar; some sugarsExample: Formaldehyde

Polar, acidic; fats and amino acidsExample: Acetic acid

Polar, basic; amino acidsExample: Tryptophan

Disulfide Bonds; some amino acidsExample: Ethanethiol

Polar, forms H-bonds; some sugarsand amino acids; Example: Ethanol

Polar; some sugarsExample: Formaldehyde

Polar; some sugarsExample: Acetone

Polar, acidic; fats and amino acidsExample: Acetic acidDisulfide Bonds; some amino acidsExample: Ethanethiol

Functional Groups

Functional Groups• The symbol “R” is used to

represent any carbon chains or rings

Alcohols

• Alcohols - a class of organic compounds with an -OH group–The -OH functional group in alcohols

is called a “hydroxyl” group; thus R-OH is the formula

• How is this different from the hydroxide ion? (covalent bonding with the carbon- not ionic with a metal like bases)

Alcohols• Aliphatic alcohols classified into

categories according to the number of R groups attached to the carbon with the hydroxyl–1 R group: primary alcohol–2 R groups: secondary alcohol–3 R groups: tertiary alcohol

Alcohols• Both IUPAC and common names• For IUPAC:

–drop the -e ending of the parent alkane name; add ending of -ol, number the position of -OH

–parent is the longest chain that contains the carbon with the hydroxyl attached.

Alcohols

• The hydroxyl is given the lowest position number

• Alcohols containing 2, 3, and 4 of the -OH substituents are named diols, triols, and tetrols respectively

Alcohols• Common names:

–similar to halocarbons, meaning name the alkyl group, then followed by the word alcohol

–One carbon alcohol = methyl alcohol

Alcohols

• More than one -OH substituents are called glycols (ethylene glycol?)

• Phenols - compounds in which a hydroxyl group is attached directly to an aromatic ring.

• Cresol is the common name of o, m, and p isomers of methylphenol

Properties of Alcohols

• Much like water, alcohols are capable of hydrogen bonding between molecules–this means they will boil at a higher

temp. than alkanes and halocarbons with a comparable number of atoms


• Alcohols are derivates of water; the -OH comes from water, and thus are somewhat soluble

• Alcohols of up to 4 carbons are soluble in water in all proportions; more than 4 carbons are usually less soluble, because the longer carbon chain is more nonpolar


• Many aliphatic alcohols used in laboratories, clinics, and industry–Isopropyl alcohol (2-propanol) is

rubbing alcohol; used as antiseptic, and a base for perfume, creams, lotions, and other cosmetics

• Ethylene glycol (1,2-ethanediol) - commonly sold as “antifreeze”


• Glycerol (1,2,3-propanetriol) - used as a moistening agent in cosmetics, foods, and drugs; also a component of fats and oils

• Ethyl alcohol (ethanol) used in the intoxicating beverages; also an important industrial solvent


• Denatured alcohol- means it has been made poisonous by the addition of other chemicals, often methyl alcohol (methanol, or wood alcohol).

• As little as 10 mL of methanol has been known to cause permanent blindness, and 30 ml has resulted in death!

Ethers

• A class of organic compounds in which oxygen is bonded to 2 carbon groups: R-O-R is formula

• Naming? The two R groups are alphabetized, and followed by ether

• Two R groups the same? Use the prefix di-

Ethers

• Diethyl ether is the one commonly called just “ether”–was the first reliable general

anesthetic–dangerous- highly flammable, also

causes nausea• ethers are fairly soluble in water

Aldehydes and Ketones• Review:

–alcohol has an oxygen bonded to a carbon group and a hydrogen

–ether has an oxygen bonded to two carbon groups

• An oxygen can also be bonded to a single carbon by a double bond

Aldehydes and Ketones

• The C=O group is called the “carbonyl group”– it is the functional group in both

aldehydes and ketones• Aldehydes - carbonyl group always

joined to at least one hydrogen (meaning it is always on the end!)

A. Aldehydes and Ketones – Aldehyde – carbonyl group always appears on the end of the

hydrocarbon chain and has at least one H atom bonded to the carbonyl group


• Ketones - the carbon of the carbonyl group is joined to two other carbons (meaning it is never on the end)

Aldehydes and Ketones• Naming?

–Aldehydes: identify longest chain containing the carbonyl group, then the -e ending replaced by -al, such as methanal, ethanal, etc.

Ketones: longest chain w/carbonyl, then new ending of -one; number it?

propanone, 2-pentanone, 3-pentanone


• Neither can form intermolecular hydrogen bonds, thus a much lower b.p. than corresponding alcohols

• wide variety have been isolated from plants and animals; possible fragrant odor or taste; many common names


• Benzaldehyde• Cinnamaldehyde• Vanillin• Methanal (the common name is:

formaldehyde)–40% in water is formalin, a

preservative


• Propanone (common: acetone) is a good solvent; miscible with water in all proportions

• why is it a good substance used in nail-polish removers? (a powerful solvent-able to dissolve both polar & nonpolar)

The Carboxylic Acids…

• Also have a carbonyl group (C=O), but is also attached to a hydroxyl group (-OH) = “carboxyl” group

• general formula: R-COOH–weak acids (ionize slightly)

• Named by replacing -e with -oic and followed by the word acid

• methanoic acid; ethanoic acid

Carboxylic Acids

• Abundant and widely distributed in nature, many having a Greek or Latin word describing their origin–acetic acid (ethanoic acid) from

acetum, meaning vinegar–many that were isolated from fats

are called fatty acids

C. Carboxylic Acids and Esters

The Esters…

• General formula: RCOOR• Derivatives of the carboxylic acids, in

which the -OH from the carboxyl group is replaced by an -OR from an alcohol:carboxylic acid + alcohol ester + water

• many esters have pleasant, fruity odors- banana, pineapple, perfumes

C. Carboxylic Acids and Esters

• Esters – a carboxylic acid reacts with an alcohol to form an ester and a water molecule

– General formula

C. Carboxylic Acids and Esters • To name esters

– Use the alkyl name from the alcohol followed by the acid name, where the –ic ending is replaced by –ate.

isopropylethanoate

Esters

• Although polar, they do not form hydrogen bonds (reason: there is no hydrogen bonded to a highly electronegative atom!)–thus, much lower b.p. than the

hydrogen-bonded carboxylic acids they came from

Esters

• Can be prepared from a carboxylic acid and an alcohol; usually a trace of mineral acid added as catalyst (because acids are dehydrating agents)

Esters

• Naming? It has 2 words:–1st: alkyl attached to single

bonded oxygen from alcohol–2nd: take the acid name, remove

the -ic acid, add -ate

Organic NomenclatureSuffixes/Meanings I

• -ane Alkane (saturated hydrocarbon)• -ene Alkene (one double bond) • -yne Alkyne (one triple bond)• -ine organic amine (amphetamine,

caffeine, cocaine, morphine, heroin)

• -one Ketone (acetone, nail polish remover)

Organic NomenclatureSuffixes/Meanings II

• -ase Enzymes ( protein catalysts in biochemical

reactions)

• -ose Sugars (glucose, sucrose)• -ol Alcohols• -al Aldehydes

(formaldehyde)• -ate Esters (many flavors and

fragrances)• -adeSomething to drink

Organic Chemistry CH. 25. Definitions Organic means “based on carbon” Hydrogen, oxygen, and...

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Transcript of Organic Chemistry CH. 25. Definitions Organic means “based on carbon” Hydrogen, oxygen, and...