380 likes | 617 Vues
2.11 IUPAC Nomenclature of Unbranched Alkanes. Table 2.2 IUPAC Names of Unbranched Alkanes. Retained: methane CH 4 ethane CH 3 CH 3 propane CH 3 CH 2 CH 3 butane CH 3 CH 2 CH 2 CH 3. Table 2.2 IUPAC Names of Unbranched Alkanes. Note: n -prefix is not part of IUPAC name of any alkane.
E N D
Table 2.2IUPAC Names of Unbranched Alkanes • Retained: • methane CH4 • ethane CH3CH3 • propane CH3CH2CH3 • butane CH3CH2CH2CH3
Table 2.2IUPAC Names of Unbranched Alkanes • Note:n-prefix is not part of IUPAC name of any alkane. • For example: n-butane is "common name" for CH3CH2CH2CH3;butane is "IUPAC name." • Others: • Latin or Greek prefix for number of carbons + ane suffix
Table 2.2IUPAC Names of Unbranched Alkanes • Number of carbons Name Structure • 5 pentane CH3(CH2)3CH3 • 6 hexane CH3(CH2)4CH3 • 7 heptane CH3(CH2)5CH3 • 8 octane CH3(CH2)6CH3 • 9 nonane CH3(CH2)7CH3 • 10 decane CH3(CH2)8CH3
Table 2.2IUPAC Names of Unbranched Alkanes • Number of carbons Name Structure • 11 undecane CH3(CH2)9CH3 • 12 dodecane CH3(CH2)10CH3 • 13 tridecane CH3(CH2)11CH3 • 14 tetradecane CH3(CH2)12CH3 • 15 pentadecane CH3(CH2)7CH3 • 16 hexadecane CH3(CH2)8CH3
Table 2.2IUPAC Names of Unbranched Alkanes • Number of carbons Name Structure • 17 heptadecane CH3(CH2)15CH3 • 18 octadecane CH3(CH2)16CH3 • 19 nonadecane CH3(CH2)17CH3 • 20 icosane CH3(CH2)18CH3 • 25 pentacosane CH3(CH2)22CH3 • 30 triacontane CH3(CH2)28CH3
The C6H14 Isomers CH3CH2CH2CH2CH2CH3 (CH3)2CHCH2CH2CH3 (CH3CH2)2CHCH3 (CH3)2CHCH(CH3)2 (CH3)3CCH2CH3
The C6H14 Isomers CH3CH2CH2CH2CH2CH3 • The IUPAC name of the unbranched alkanewith a chain of 6 carbons is hexane. Hexane
IUPAC Nomenclature of Branched Alkanes (Table 2.6) • Step 1) Find the longest continuous carbonchain and use the IUPAC name of theunbranched alkane as the basis. • Step 2) Add name of substituent as a prefix. • Step 3) Number the chain from the end nearestthe substituent, and identify the carbon to which the substituent is attached by number.
The C6H14 Isomers (CH3)2CHCH2CH2CH3 2-Methylpentane (CH3CH2)2CHCH3 3-Methylpentane
The C6H14 Isomers (CH3)2CHCH(CH3)2 • Use replicating prefixes (di-, tri-, tetra-, etc.) according to the number of identical substituentsattached to the main chain. 2,3-Dimethylbutane (CH3)3CCH2CH3 2,2-Dimethylbutane
H CH3 H C H H H H CH3CH2 C C H H Methyl and Ethyl Groups or Methyl or Ethyl
R H R Unbranched Alkyl Groups • If potential point of attachment is at the endof the chain, take the IUPAC name of thecorresponding unbranched alkane and replacethe -ane ending with -yl.
R H R H H H H H CH3CH2CH2CH2 C C C C H H H H Unbranched Alkyl Groups • If potential point of attachment is at the endof the chain, take the IUPAC name of thecorresponding unbranched alkane and replacethe -ane ending with -yl. or Butyl
CH3(CH2)4CH2 CH3(CH2)5CH2 CH3(CH2)16CH2 Unbranched Alkyl Groups Hexyl Heptyl Octadecyl
The C3H7 Alkyl Groups H H H or H CH3CH2CH2 C C C H H H and H H H or H CH3CHCH3 C C C H H H
The C3H7 Alkyl Groups H H H • IUPAC name: Propyl • Common name: n-Propyl or H CH3CH2CH2 C C C H H H
Naming Alkyl Groups (Table 2.7) • Step 1: Identify longest continuous chain starting at point of attachment. • Step 2: Drop -ane ending from name of unbranched alkane having same number of carbons as longest continuous chain and replace with -yl. • Step 3: Identify substituents on longest continuous chain. • Step 4: Chain is always numbered starting atpoint of attachment.
H H H or H CH3CHCH3 H C C C H H The C3H7 Alkyl Groups • IUPAC name: 1-Methylethyl • Common name: Isopropyl
H H H or H CH3CH2CH2 C C C H H H The C3H7 Alkyl Groups • Classification: Primary alkyl group • Alkyl groups are classified according to thedegree of substitution at the carbon that bears thepoint of attachment. A carbon that is directlyattached to one other carbon is a primary carbon.
H H H or H CH3CHCH3 H C C C H H The C3H7 Alkyl Groups • Classification: Secondary alkyl group • Alkyl groups are classified according to thedegree of substitution at the carbon that bears thepoint of attachment. A carbon that is directlyattached to two other carbons is a secondary carbon.
H H H H or H CH3CH2CH2CH2 C C C C H H H H The C4H9 Alkyl Groups • IUPAC name: Butyl • Common name: n-Butyl • Classification: Primary alkyl group
1 3 2 The C4H9 Alkyl Groups H H H H • IUPAC name: 1-Methylpropyl • Common name: sec-Butyl • Classification: Secondary alkyl group or H H CH3CHCH2CH3 C C C C H H H
CH3 1 3 2 CH3 C CH2 H The C4H9 Alkyl Groups • IUPAC name: 2-Methylpropyl • Common name: Isobutyl • Classification: Primary alkyl group
The C4H9 Alkyl Groups • IUPAC name: 1,1-Dimethylethyl • Common name: tert-Butyl • Classification: Tertiary alkyl group CH3 1 2 CH3 C CH3
Branched Alkanes • Octane
Branched alkanes • 4-Ethyloctane
Branched Alkanes • 4-Ethyl-3-methyloctane List substituents in alphabetical order.
Branched Alkanes • 4-Ethyl-3,5-dimethyloctane List substituents in alphabetical order. But don't alphabetize di-, tri-, tetra-, etc.
First Point of Difference Rule 5 3 4 6 1 8 7 2 6 2 3 7 4 5 8 1 • The chain is numbered in the direction that gives the lower locant to the substituent at the first point of difference in the names. • Don't add locants! What is the correct name? 2,3,3,7,7-Pentamethyloctane? 2,2,6,6,7-Pentamethyloctane?
First Point of Difference Rule 5 3 1 7 6 2 4 8 • The chain is numbered in the direction that gives the lower locant to the substituent at the first point of difference in the names. • Don't add locants! What is the correct name? 2,2,6,6,7-Pentamethyloctane?
Cycloalkanes • Cycloalkanes are alkanes that contain a ring of three or more carbons. • Count the number of carbons in the ring, and add the prefix cyclo to the IUPAC name of the unbranched alkane that has that number of carbons. Cyclopentane Cyclohexane
CH2CH3 Cycloalkanes • Name any alkyl groups on the ring in the usual way. Ethylcyclopentane
H3C CH3 CH2CH3 Cycloalkanes • Name any alkyl groups on the ring in the usual way. • List substituents in alphabetical order and countin the direction that gives the lowest numericallocant at the first point of difference. 3-Ethyl-1,1-dimethylcyclohexane