Chem 1152: Exam 2 Review Naming Compounds.

Chem 1152: Exam 2 Review

Naming Compounds

Naming alkanes – Rules Rules for naming alkanes have been standardized by IUPAC (International Union of Pure and Applied Chemistry) Prefix-------------------------------------------- Parent--------------------------------- Suffix Substituents Longest C Chain Family (Functional class) (# and ID of attached groups) How to name an alkane 1. Find the longest continuous C chain. This is the Parent.

If 2 different chains of equal length are present, the parent is the one with the MOST branch points.

2. Number the atoms in the parent chain. Begin numbering at the end nearest the 1st branch point. If 1st point is the same at either end, begin at end nearest the 2nd, 3rd branch points. We want to label this so that branch points are the lowest numbers possible.

3. Identify and number the substituents. Assign a number to each substituent based on carbon number in parent chain. Two substituents on the same carbon (not 3) get the same number. If both substituents are the same, use the prefix di-. If structure has multiple identical substituents, put them altogether in the name. For

example: 2,3,4,5,6-pentamethyloctane. 4. Write name as a single word.

Separate prefixes with hyphens. Use commas (no spaces) to separate numbers. If 2 or more different substituents are present, cite in alphabetical order. Multiplier prefixes (di-, tri-, tetra-, penta-, etc.) are NOT used for alphabetizing. The prefixes sec- and t- are NOT used for alphabetizing, but iso- IS used for

alphabetizing.

Rules for naming cycloalkanes 1. Substituents are named so that the first one is determined alphabetically. 2. After the first one is identified, the others are numbered to get the lowest possible

sequence of numbers.

Cl

CH3

1

2

Cl

CH3

CH3

1

23

chloro-3-methylcyclopentane chloro-2,3-dimethylcyclopentane

Naming Alkenes

1. Name the longest chain that contains the double bond or double bonds. The name of the chain will end in –ene.

2. Number this longest chain so the C=C bond or bonds has/have the lowest number.

3. The first C of the C=C bond (for C=C bond to have lowest number) identifies the positional location of the double bond.

4. Name the attached functional groups. 5. Combine the names of the attached groups and longest chain, the same as

you would with alkanes.

Naming Alkynes

1. Name of cmpd ends in yne. 2. The longest chain chosen for the root name must include both carbon

atoms of the triple bond. 3. The root chain must be numbered from the end nearest a triple bond

carbon atom. a. If the triple bond is in the center of the chain, the nearest substituent

rule is used to determine the end where numbering starts. 4. The smaller of the two numbers designating the carbon atoms of the triple

bond is used as the triple bond locator. 5. If several multiple bonds are present, each must be assigned a locator

number. Double bonds precede triple bonds in the IUPAC name, but the chain is numbered from the end nearest a multiple bond, regardless of its nature. The name will then have multiplier prefix (e.g., diyne, triyne, etc.)

6. Because the triple bond is linear, it can only be accommodated in rings larger than ten carbons. In simple cycloalkynes the triple bond carbons are assigned ring locations #1 and #2. Which of the two is #1 may be determined by the nearest substituent rule.

7. Substituent groups containing triple bonds are: HC≡C– Ethynyl group HC≡CH–CH2– Propargyl group

Rules for naming alcoholsRules for naming alcohols

For single hydroxy (-OH) group•Step 1: Identify longest chain that includes (-OH) group. Drop –e from hydrocarbon name, and replace with ending –ol.•Step 2: Number this parent chain to give lowest number to carbon with attached (-OH) group.•Step 3: Locate position of (-OH) group.•Step 4: Locate and name all branches attached to parent chain.•Step 5: Include names of all branches (still in alphabetical order) in prefix of compound name. Include location of (-OH) group.•Note: Multiple (-OH) groups are named by addiing diol, triol, etc, to end of alkane without removing -e.

CH3

CH3

OH1

253

4

2-ethyl-1-pentanol

OHOH

CH3

12 3

4

2-methyl-1,4-butanediol

Naming AlcoholsNaming Alcohols

CH3

CH3

CH3

CH3

OHCH3

2,2,4-trimethyl-3-hexanol

OH

CH3

CH3 OH

CH3

3-butyl-2,4-hexanediol

OH

OH

1,2-cyclohexanediol

CH3 CH3

CH3

OH

3-methyl-3-pentanol

OH

Br

CH3

5-bromo-3-ethyl-1-pentanol

CH3CH3

CH3

OH

2-isopropyl-1-methylcyclopropanol

OH

CH3CH3

2,2-dimethylcyclopentanol

OH

OHOH

CH3

1,2,4-hexanetriol

OH

3-phenyl-1-propanol

EthersEthers• Ether: Oxygen with carbon attached on either side.• Naming ethers• Common Names

1. Name the two groups attached to the oxygen then add the word ether2. If both groups the same, can be named with prefix di-.

• IUPAC Names– O-R group is alkoxy.– The –yl ending of smaller R group is replaced by –oxy.

CH3

O CH3

CH3 OCH3

CH3

OCH3

butyl methyl ether

ethyl propyl ether

dipropyl ether

CH3

CH3 OCH3

isopropyl propyl ether 1-methoxybutane

1-ethoxypropane

1-propoxypropane

1-isopropoxypropaneCl

CH3

CH3 OCH3

2-chloro-1-isopropoxypropane

OCH3

CH3

p-methoxytoluene

CH3

CH3

CH3 O

CH3

CH3

2-methoxy-3,4-dimethylhexane

ThiolsThiols• Thiols: Sulfur analogs of alcohols (-SH instead of –OH)• Chemically- similar (i.e., form similar compounds)• More volatile (lower BP) than alcohols but less water-soluble• Thiols stink!

– This is how skunks defend themselves– Chopped onions emit propanethiol– Thiols found in garlic– Ethanethiol added to natural gas (methane) so you can smell a leak

• IUPAC Names for simple thiols– The –SH group is a sulfhydryl group.– Follow the same steps for naming as you do for alcohols, but do not modify alkane

ending; instead add –thiol to end of parent.

SH

CH3

SH

CH3CH3

SH

CH3

CH3

CH3

butanethiol 2-butanethiol 2-methyl-3-hexanethiol

Naming AldehydesNaming Aldehydes

O

HCH3

pentanal

Cl

O

H

5-chloropentanal

CH3

O

H

Cl

5-chloro-4-ethylpentanal

H O

CH3CH3

2-ethylbutanal

CH3

O

H

CH3

CH3

3,4-dimethylhexanal

Cl

CH3 O

H

5-chloro-2-methylbenzaldehydeCl

O

H

m-chloro-benzaldehyde

CH3

O

CH3 O

H

5-methoxy-2-methylbenzaldehyde

Naming KetonesNaming Ketones

2-pentanone 5-chloro-2-pentanone 1-chloro-3-pentanone

4-ethylcyclohexanone 2-fluoro-5-methyl-4-hexanone

O

CH3 CH3

Ketone: Carbonyl group with two C attached.•Named by replacing –e with –one (IUPAC).•Numbered from end closest to carbonyl group

ClO

CH3

O

Cl

CH3

O

CH3CH3

F O

CH3

CH3

Chem 1152: Exam 2 Review

Reactions

Addition reactions to alkenesAddition reactions to alkenes

Halogenation: Addition of a Halide (fluorine, chlorine, bromine, iodine)

CH2CH3CH2CH Br-Br

Br

+ CH2CH3CH2CH

Br1-butene 1,2-dibromobutane

Hydrogenation: Use of metal catalyst (Pt, Pd, Ni) to add H

CHCH3CH3CH

H

+

H2-butene butane

H2 CHCH3CH3CH

Addition reactions to alkenesAddition reactions to alkenesAcid Rxn: (HCl, HBr, etc.)

CHCH3CH2

Br+

HHBr

CHCH3CH2

H Br

CHCH3CH2

1-bromopropane

2-bromopropane

The major product of this rxn is 2-bromopropane, not 1-bromopropane. This is due to: Markovnikov’s rule: When H-X reacts with alkene, H goes to C that already has the most H.

Hydration: Water may react with alkene in presence of acid catalyst

CH2CH3CH + H-OHOH H

H2SO4 CH2CH3CH

Alcohol ReactionsAlcohol Reactions

1. Alcohol Dehydration (Elimination Rxn):

H-OHH2SO4

R

OH

RR

HR 180 C

+

R

RR

R

• Alcohol Hydration (Addition Rxn)R

RR

R

H-OH+H2SO4

R

OH

RR

HR

Alcohol Dehydration to produce alkeneAlcohol Dehydration to produce alkene• Alcohol Dehydration (Elimination Rxn):

OH

CC

CC

H

HH

HH

HH

HH

H2SO4

180 oC

CC

C

CH

HH

H

H

H

HH

CC

CC

H

HH

HH

H

H

H

H-OH+

H-OH+

2-butene

1-butene

This rxn (at 180 °C) generates 2 products: 2-butene and 1-butene. The major product is 2-butene (90%) because both C=C bond carbons are

attached to at least one other carbon. The minor product is 1-butene (10%) because only one of the C=C bond

carbons is attached to at least one other carbon. The major product in these rxns will always be the one resulting in the

highest number of carbon groups bonded to the C=C carbons.

Alcohol Dehydration to produce etherAlcohol Dehydration to produce ether• Alcohol Dehydration (Elimination Rxn):

This rxn (at 140 °C) generates an ether and water. This rxn works mainly with primary alcohols.

H2SO4

140 oCR

OH H

R

O+ R

R

O

H

OH+

etheralcohol alcohol

Primary (1°)R O

H H

H

OH

H HH

Hydroxy bearing C is attached to either 0 or 1 other C

H2SO4

140 oCOHCH3 +

H

OH+CH3H

O OCH3

CH3

H2SO4

140 oCOHCH3

H

OH+CH3OCH3

H-OH+RC

O

HH

H

(O)+ R C

O

H

(O)R C

O

OH

Alcohol Oxidation for Primary AlcoholAlcohol Oxidation for Primary Alcohol

Carboxylic acid

Primary alcoholaldehyde

Immediate product of oxidation of primary alcohol is aldehyde, which is then readily further oxidized to a carboxylic acid.

The aldehyde product may be isolated before further oxidation by maintaining high temp. and boiling aldehyde out of rxn mixture.

This is possible because aldehydes do not H-bond like alcohols and carboxylic acids.

H-OH+RC

O

HR

H

(O)+ R C

O

R

Alcohol Oxidation for Secondary and Tertiary AlcoholsAlcohol Oxidation for Secondary and Tertiary Alcohols

Secondary alcohol ketone

Product of oxidation of secondary alcohol is a ketone, which resists further oxidation.

NO RXNR

CO

RR

H

(O)+

Tertiary alcohol

Multistep RxnsMultistep Rxns The synthesis of most alcohols may require multiple steps (i.e., to get

product X from reactant A, a product (B, C …X) must be created). To solve these problems, work backwards from the final product.

O

OOH (O)+ H-OH+

Oxidize 2° alcohol to form ketone.

+ OHH-OHH2SO4

Use acid-catalyzed hydration (addition) to form alcohol.

+ OHH-OHH2SO4

(O)+ O H-OH+

The completed series of rxns.

Hydrogenation Rxn – AldehydesHydrogenation Rxn – AldehydesAldehyde hydrogenation rxnAldehyde hydrogenation rxn

Alcohol oxidation rxnAlcohol oxidation rxn

H-OH+RC

O

HH

H

(O)+ R C

O

H

(O)R C

O

OH

Carboxylic acid

Primary alcoholaldehyde

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

Hydrogenation Rxns – KetonesHydrogenation Rxns – KetonesKetone hydrogenation rxnKetone hydrogenation rxn

H-OH+RC

O

HR

H

(O)+ R C

O

R

Secondary alcohol ketone

Alcohol oxidation rxnAlcohol oxidation rxn

Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7th Edition, 2011

Addition of alcohol to aldehydes and ketonesAddition of alcohol to aldehydes and ketones

Hemiacetal is unstable, hard to isolate. With excess alcohol and an acid catalyst, a stable acetal is formed.

Note the bidirectional arrows

O

R H

+ H

R

O

RO

HO

R H

H+, RO-H

RO

RO

R H + H-O-H

Hemiacetal Hemiacetal intermediateintermediate

acetalacetal

O

R R

+ H

R

O

RO

HO

R R

H+, RO-H

RO

RO

R R + H-O-H

Hemiketal Hemiketal intermediateintermediate

ketalketal

Hydrolysis of acetals and ketalsHydrolysis of acetals and ketals

“Cutting by water” is essentially the reverse of the addition of alcohol to either aldehyde or ketone.

aldehydealdehydeacetalacetal

RO

RO

R H +H

H

O H+ O

R H

2 R-OH+

alcoholalcohol

ketoneketoneketalketal alcoholalcohol

RO

RO

R R +H

H

O H+ O

R R

2 R-OH+

Intramolecular addition of alcohols to aldehydeIntramolecular addition of alcohols to aldehyde

C1 is hemiacetal carbon. Attached to it you will find: H, OH, OR and R, just like non-cyclical compounds.

Intramolecular Intramolecular hemiacetalhemiacetalglucoseglucose

C

C

C

C

CH2

C

OH

OH

OH

OH

HO H

H

H

H

H O1

2

3

4

5

6

*CH2OH

C

C

C C

O

C

6

5

4

3 2

1

OH

H

OH

OH

OH

H

H

H

H

Aldehyde Rxns – Testing for AldehydesAldehyde Rxns – Testing for Aldehydes

Benedict’s Reagent reacts with aldehydes that have an alcohol on the adjacent carbon (e.g., glucose)

Products include a red precipitate of copper (I) oxide

Tollens’ Reagent (reacts with all aldehydes)Tollens’ Reagent (reacts with all aldehydes)

Benedict’s Reagent (reacts with some aldehydes)Benedict’s Reagent (reacts with some aldehydes)