NOMENCLATURE Dr. Sheppard CHEM 2411 Spring 2015 Klein (2 nd ed.) sections 4.1, 4.2, 4.14, 7.2, 8.3, 8.4, 10.2, 13.1, 14.2, 14.11, 18.2, 20.2, 21.2, 21.6,

NOMENCLATURE

Dr. Sheppard

CHEM 2411

Spring 2015

Klein (2nd ed.) sections 4.1, 4.2, 4.14, 7.2, 8.3, 8.4, 10.2, 13.1, 14.2, 14.11, 18.2, 20.2, 21.2, 21.6, 23.2, Appendix

Nomenclature• The naming of organic molecules• 1800s: named by discoverers

• 1892: IUPAC system

Nomenclature• All names have Substituents-MainChain• Substituents are groups attached to the main chain• MainChain consists of Parent-Infix-Suffix

• Parent tells you number of carbons in main chain• Infix tells you if the carbon-carbon bonds are single bonds

(saturated molecule) or double or triple bonds (unsaturated molecules)

• Suffix tells you the functional group of your molecule

ParentNumber of carbons Parent name

1 meth-

2 eth-

3 prop-

4 but-

5 pent-

6 hex-

7 hept-

8 oct-

9 non-

10 dec-

11 undec-

12 dodec-

Infix• “-an-” = only carbon-carbon single bonds (saturated)• “-en-” = an alkene (double bond) is present (unsaturated)• “-yn-” = an alkyne (triple bond) is present (unsaturated)

SuffixFunctional group Suffix

alcohol -ol

ether ether

amine -amine

nitrile -nitrile

thiol -thiol

sulfide sulfide

aldehyde -al

ketone -one

carboxylic acid -oic acid

ester -oate

amide -amide

acid chloride -oyl chloride

acid anhydride -oic anhydride

Straight-chain Alkanes• Main chain = carbon chain• Infix = “-an-”• Suffix = “-e”• No substituents

Nomenclature• Consider the molecule 2-hexanol.

• How many carbons in the main chain?• Saturated or unsaturated?• What functional group?

• Consider the molecule octanoic acid.• How many carbons in the main chain?• Saturated or unsaturated?• What functional group?

• Consider the molecule 4-methyl-2-pentanamine.• How many carbons in the main chain?• Saturated or unsaturated?• What functional group?• What is 4-methyl?

Substituents• Groups off of main chain (branches)• Parts of larger compounds (not stable by themselves)• Alkyl groups = Alkane – H• “-ane” changes to “-yl”• Methyl

• methane – H • CH4 – H

• CH3─

• Ethyl• ethane – H • CH3CH3 – H

• CH3CH2─

Substituents• Propane – H gives two possible alkyl groups

• Propyl• Isopropyl

• Similarly, there are multiple alkyl groups with 4 carbon atoms, 5 carbon atoms, etc.

Alkyl groups you need to know

• Methyl• Ethyl• Propyl• Isopropyl• Butyl• Isobutyl • sec-butyl• tert-butyl (t-butyl)

• Pentyl (amyl)• Isopentyl (isoamyl)• Neopentyl • tert-pentyl• Hexyl, heptyl, etc.• Halogens

• Fluoro• Chloro• Bromo• Iodo

Naming alkanes

1. Find the parent chain• Longest continuous chain of C atoms• Name of chain = parent name• If 2 chains of equal length, parent is the chain with more

substituents

2. Number each carbon in the parent chain• Start from the end closest to the first substituent• If there are substituents equal distance from both ends, number

from the end nearest the second substituent

Naming alkanes, cont.

3. Name and number substituents• Name = alkyl group name• Number = point of attachment to parent chain• Two substituents on the same C get the same number

4. Write the name as a single word• Substituents before parent name (include #)• Separate # and word with hyphen• Separate two numbers with a comma• List substituents in alphabetical order• Multiple identical substituents use prefixes di, tri, tetra, penta, hexa• DO NOT use sec, tert, di, tri, etc. when alphabetizing• DO use iso, neo when alphabetizing

ExamplesStructure Name

CH3 CH2 CH

CH3

CH3

CH3 CH CH2 CH

CH3 CH3

CH3

CH3 CH CH2 CH

CH2 CH3

CH3

CH3

Examples• Draw 3-ethylpentane.

• Draw all the constitutional isomers with the molecular formula C6H14. Name each isomer.

Examples

Structure Name

CH3 CH CH

CH2CH2CH3

CH2CH3

CH2CH3

CH3 CH CH2 CH

CH3 CH2CH3

CH2CH3

CH3CH2 CH CH

CH

CH2CH2CH3

CH3

CH3

CH

CH3CH3

ExamplesStructure Name

CH3 C CH2

CH3

CH3

CH

CH2CH3

CH2CH3

CH3 CH2 CH

CH3

CH

CH3

CH2 CH2 CH

CH3

CH2CH3

CH3 CH CH2 CH2

CH3

CH

Br

CH3

Naming Cycloalkanes• Unsubstituted cycloalkanes:

• Add “cyclo” to the parent name

• Bicycloalkanes• Two rings• Most common is norbornane

• Bicyclo[2.2.1]heptane

Naming Cycloalkanes• Substituted cycloalkanes:

• Parent = ring or substituent (whichever has more carbons)

• Number the substituents• Do not need to show number if only one substituent on a ring• If two substituents, start with the first alphabetically, number in the

direction of the second substituent• If more than two substituents, number so that the substituents have the

lowest set of numbers

ExamplesStructure Name

CH2CH3

CH3

CH3

ExamplesStructure Name

CH2CH3

CH3

CH3

CH3

CH3

Br

Cycloalkane Stereoisomers• Cycloalkanes are roughly planar• Substituents are either above or below this plane

• Shown with dash and wedges• Dash = back; wedge = forward

• In a disubstituted cycloalkane, two substituents on the same side (both back or both forward) are cis. Two substituents on opposite sides (one back, one forward) are trans.

• Cis and trans versions of the same molecule are stereoisomers• Same molecular formula• Same connectivity• Different 3D orientation• Cannot be converted

by bond rotation

CH3

CH3

CH3CH3

CH3 CH3

cis trans

CH3

CH3

Examples

Structure Name

• Do these pairs represent constitutional isomers, cis-trans stereoisomers or the same compound?

(a)

(b)

CH3

CH2CH2CH3

Alkene Nomenclature• Similar to alkanes• Change infix from “-an-” to “-en-”

CH2 CH2 CH CH2CH3

ethene (ethylene) propene (propylene)

Naming Alkenes• For larger alkenes:

1. Parent is longest C chain containing both carbons of C=C

2. Number chain so C=C has lowest possible number• If the double bond is equidistant from both ends, start numbering at

end nearest the first substituent• Show location of C=C by first number• Alkenes with >1 C=C use “-adiene”, “-atriene”, etc. in place of “-

ene” and show location of all double bonds

3. Name and number substituents and write the full name

• Example: CH3 CH CH CH2

CH2 CH2 CH2

CH3

ExamplesStructure Name

Structure Name

Cycloalkenes• The carbon atoms of the C=C are numbered 1 and 2• Number ring in direction to give first substituent lowest

possible number

CH3

CH3CH2

Alkene substituents

Substituent Name

CH2═ methylene

CH2═CH─ vinyl

CH2═CH─CH2─ allyl

Alkene Stereoisomers• Cis-trans stereoisomers• Seen with disubstituted alkenes• Cis means groups are on the same side of the double

bond; trans means groups are on opposite sides • Cannot convert through bond rotation• Example: 2-butene

CH3

HCH3

HH

CH3CH3

H

cis-2-butene trans-2-butene

Examples• Are the following alkenes cis, trans, or neither?

(a)

(b)

(c)

H

CH3

H

CH3

CH3H

H

Alkyne Nomenclature• Similar to alkenes• Change infix from “-en-” to “-yn-”

C CHCH3

ethyne (acetylene) propyne

CH CH

Naming Alkynes• For larger alkynes:

1. Parent is longest C chain containing both carbons of C≡C

2. Number chain so C≡C has lowest possible number• If the triple bond is equidistant from both ends, start numbering at

end nearest the first substituent• Show location of C≡C by first number• Alkynes with >1 C≡C use “-adiyne”, “-atriyne”, etc. in place of “-yne”

and show location of all double bonds

3. Name and number substituents and write the full name

• Example:

CH3 C C CH2 CH CH3

CH3

Enyne• Contains both alkene and alkyne• Number from end closest to first multiple bond (either

C=C or C≡C) and show both numbers• If the C=C and C≡C are equidistant from the ends, C=C

gets the lower number• Examples:

Structure Name

CH2 CH CH2 CH2 C C H

CH CH CH C C HCH3

CH3

Naming Aromatic Compounds • Benzene

• Monosubstituted benzenes• Substituent name + “benzene”

Common Benzene Compounds

Benzene Nomenclature• If substituent has greater than 6 carbons, it becomes the

parent, and benzene is called a phenyl group

• Benzene substituents:

2-phenylheptane

Disubstituted Benzenes• ortho (1,2)• meta (1,3)• para (1,4)

Br

Br

Br

Br

Br

Br

1,4-dibromobenzene

1,3-dibromobenzene1,2-dibromobenzene

p-dibromobenzene

m-dibromobenzeneo-dibromobenzene

Naming Disubstituted Benzenes• If one substituent is part of a common name, that name is

the parent and that substituent is at carbon 1

• If neither substituent is part of a common name, list the substituents in alphabetical order (first alphabetically is at carbon 1)

• If both substituents are part of common name, use this order of priority to determine the parent name:

-CO2H > -CHO > -OH > -NH2 > -CH3

ExamplesStructure Name

CO2H

Cl

CH2CH3

Cl

CO2H

NH2

ExamplesStructure Name

NH2

NH2

CH3

NH

CH3

Naming Polysubstituted Benzenes• With 3 or more substituents do not use ortho, meta, para• Number ring to give smallest set of numbers• If a common name, use as parent (substituent at carbon 1)• List substituents in alphabetical order

Examples

Structure Name

Br Br

OH

Br

Cl

CH2CH3

NO2

CH3

NO2

NO2

Another Aromatic Compound• Pyridine

• If substituted, nitrogen is atom 1 of the ring. Number in direction of other substituents.

N

N

CH3

3-methylpyridine

Naming Alcohols• Acyclic alcohols

1. Parent chain is longest chain containing C bonded to –OH

2. Change suffix from “-e” to “-ol”

3. Number from end closest to –OH. Show location of –OH.

4. Name/number substituents

• Cyclic alcohols1. Ring is the parent

2. Number ring so –OH is at carbon 1 and other substituents have lowest possible numbers. You do not need to show the location of the –OH.

3. Name/number substituents.

Naming Alcohols• Multiple hydroxyl groups

• Two –OH groups is a diol; 3 is a triol• Two adjacent –OH groups is a glycol• Name as acyclic alcohols, except keep the “-e” suffix and add “-diol”• Indicate numbers for all –OH groups

• Unsaturated alcohols (enol or ynol)1. Parent chain contains carbon bonded to –OH and both carbons of

C=C or C≡C

2. Suffix is “-ol”, infix is “-en-” or “-yn-”

3. Number chain so –OH has the lowest number

4. Show numbers for –OH and the unsaturation

5. Name/number substituents

ExamplesStructure Name

CH3 CH2 CH2 CH2 OH

CH3 CH

OH

CH2 CH3

CH3 CH

CH3

CH2 OH

OH

ExamplesStructure Name

CH3

OH

HO CH2 CH2 OH

HC C CH2 CH2 OH

OH

Naming Thiols• Thiols are sulfur analogs of alcohols• Name like alcohols, but keep the “-e” and use “-thiol” in

place of “-ol”

CH3 SH

methanethiol

SH

CH3

HS

2-butanethiol

SH

Naming Amines

1. Parent chain is longest containing C bonded to –N

2. Change suffix “-e” to “-amine”

3. Number from end closest to –N. Show location of –N.

4. Name/number substituents

NH2

2-butanamine

Examples

Structure Name

NH2

CH3 CH2 CH2 CH2 CH CH3

N

CH3 CH3

Naming Aldehydes• Parent chain contains carbon of CHO• Suffix is “-al”• CHO carbon is carbon 1 (do not need to show in name)

O

C

H H

O

C

CH3 H H

O

methanal (formaldehyde)

ethanal(acetaldehyde)

3-methylbutanal

Naming Aldehydes• Cyclic molecules with –CHO substituents

• -CHO is bonded to carbon 1 of ring• Add “carbaldehyde” to end of ring parent name

CH3 CHO

trans-4-methylcyclohexanecarbaldehyde

Naming Ketones• Parent chain contains carbon of carbonyl; suffix is “-one”• Number so carbonyl has lowest number• Cyclic ketones carbonyl is carbon 1 of the ring

• Some more common names:

O

2-propanone(acetone)

O

2-pentanone

O

CH3

O

acetophenone benzophenone

ExamplesStructure Name

H

O

CHO

CH3 CH CH CH2 C CH3

O

OCH3

Order of Precedence of Functions

• Used when more than one functional group in a molecule

• See Appendix in Klein

Functional GroupSuffix

(High Precedence)Prefix

(Low Precedence)

-CO2H -oic acid -

-CHO -al formyl-

-C(O)- -one oxo-

-OH -ol hydroxy-

-NH2 -amine amino-

Incr

easi

ng p

rece

denc

e

ExamplesStructure Name

H

OO

OH O

HO NH2

CO2HNH2

Naming Carboxylic Acids

• Parent chain contains carbon of –CO2H

• Suffix is “-oic acid”• –CO2H is carbon 1

CH3 CH

CH3

CH2 CO2H H C OH

O

CH3 C OH

O

3-methylbutanoic acid methanoic acid(formic acid)

ethanoic acid(acetic acid)

Naming Carboxylic Acids

• Cyclic molecules with –CO2H substituents• –CO2H is bonded to carbon 1 of ring

• Add “carboxylic acid” to end of ring parent name

CO2HHO

(cis)-3-hydroxycyclopentanecarboxylic acid

Examples

Structure Name

O O

OH

CO2H

Naming Acid Chlorides• Name corresponding carboxylic acid• Change “-ic acid” to “-yl chloride”• Examples:

Structure Name

CH3 C Cl

O

C Cl

O

R C

O

Cl

Naming Acid Anhydrides

• If R = R’, name carboxylic acid RCO2H. Replace “acid” with “anhydride”

• If R ≠ R’, list the two acids alphabetically and add the word “anhydride”

• Examples:

Structure Name

R C

O

O C R'

O

O O

O

CH3

O

Ph

O

O

Naming Esters• Name alkyl group bonded to oxygen (R’)• Name carboxylic acid RCO2H

• Change “-ic acid” to “-ate”• Examples:

Structure Name

R C

O

O R'

O

O

CH3 CH2 O C

O

CH3

Naming Amides• Name corresponding carboxylic acid• Change “-oic acid” to “-amide”• Examples:

Structure Name

R C

O

NH2

CH3 CH2 C

O

NH2

O

NH

O

N

Example• DMF (N,N-dimethylformamide) is a common solvent in

organic chemistry. Draw the structure of DMF.

Naming Nitriles• Two methods1. Nitrile carbon is carbon 1 of parent chain. Add “-nitrile” to end of

alkane name.

2. Name as carboxylic acid derivative. Replace “-ic acid” or “-oic acid” with “-onitrile”

C

N

4-methylpentanenitrile

CCH3 N

acetonitrile

C N

benzonitrile

Common Name System• Can be used for some simple molecules• Alkyl halides, alcohols, amines

• Name alkyl group• Add “chloride” or “bromide” or “alcohol” or “amine”

• Examples:

Structure Name

CH3Cl

(CH3)2CHBr

CH3CH2OH

CH3CH2NHCH3

(CH3CH2)2NH

Common Name System• Ketones, ethers, sulfides

• Name both alkyl groups bonded to carbonyl (ketone), oxygen (ether), or sulfur (sulfide)

• Add “ketone” or “ether” or “sulfide”

• Examples:

Structure Name

CH3 C CH3

O

O

Ph O CH2 CH3

CH3 S CH3