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Home , Alicyclic compound, Functional group, Methyl group

Ch.3 Organic Compounds: and 3.1 Functional Groups

• more than 19 million known organic compounds according to Chemical Abstracts

• classify into families with similar chemical behavior

functional groups: a group of atoms within a that has a characteristic chemical behavior ; a given , regardless of size and complexity, behaves in nearly the same way Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Br H H Br2 H H

H H H BrH

Ethylene

Br2

HO HO Br Br Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Functional Groups C/C Multiple Bonds C-Y (Y= electronegative atom: O, N, Cl, S...) C=O, C=N, C≡N

Functional Groups with C/C Multiple Bonds

CC CC CC

Alkane Arene (aromatic ring) Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Functional Groups with C-Y (Y= electronegative atom)

C X C OH CCO

(X= F, Cl, Br, I) Halide

C NH2 CSSH CC

Amine Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Functional Groups with C=O

O O O CHC CCC COHC

Aldehyde Carboxylic

O O O COC C CNC CClC

Ester chloride Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Table 3.1 Structures of Common Functional Groups

Family Functional group Simple example Name ending name structure contains only C-H and -ane CH CH C-C single bonds 3 3

-ene Alkene CC CH2=CH2 Ethene ()

-yne Alkyne CC HHCC Ethyne ()

None Arene Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Table 3.1 Structures of Common Functional Groups

Family Functional group Simple example Name ending name structure

None Halide C X (X= F, Cl, Br, I) H C Cl 3

-ol Alcohol C OH H C OH 3

-ether Ether C O C H C O CH 3 3 Dimethyl ether Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Table 3.1 Structures of Common Functional Groups

Family Functional group Simple example Name ending name structure

- Amine C NH C NH C N H3C NH2 2

- Nitrile C C N H3C C N Ethanenitrile (Acetonitrile)

None Nitro C NO H C NO 2 3 2 Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Table 3.1 Structures of Common Functional Groups

Family Functional group Simple example Name ending name structure

-thiol Thiol C SH H C SH 3 Methanethiol

-sulfide H CCHS Sulfide CCS 3 3

O O - H CCHS Sulfoxide CCS 3 3

O O - H CCHS Sulfone CCS 3 3 Dimethyl sulfone O O Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Table 3.1 Structures of Common Functional Groups

Family Functional group Simple example Name ending name structure

O O -al CHC Ethanal H3CHC ()

O O -one Ketone CCC Propanone H3CCHC 3 ()

O O -oic acid Carboxylic COHC Ethanoic acid acid H3COHC ()

O O -oate COC C Methyl ethanoate H3COC CH3 (Methyl ) Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Table 3.1 Structures of Common Functional Groups

Family Functional group Simple example Name ending name structure

O O O O -amide Amide CNHC 2 CNHC CNC Ethanamide H3CNHC 2 ()

O O -oyl chloride Carboxylic CClC Ethanoyl chloride acid chloride H3CClC ()

O O O O -oic anhydride Carboxylic COC C C Ethanoic anhydride acid anhydride H3COC CCH3 (Acetic anhydride) Ch.3 Organic Compounds: Alkanes and Cycloalkanes Practice functional Groups

O O O

HO O

Coleophomone A Ch.3 Organic Compounds: Alkanes and Cycloalkanes 3.2 Alkanes and Alkane alkanes: saturated , : aliphatic compound (meaning "")

general formula: CnH2n+2

H CCH CH CH CH CH4 3 3 3 2 3

Methane Ethane, C2H6 Propane, C3H8

C4H10 Butane Isobutane (2-Methylpropane)

Ch.3 Organic Compounds: Alkanes and Cycloalkanes

C5H12 2-Methylbutane 2,3-Dimethylpropane Ch.3 Organic Compounds: Alkanes and Cycloalkanes

- straight chain alkanes (normal alkane) - branched chain alkane

Pentane 2-Methylbutane 2,3-Dimethylpropane

C5H12

: same formula but different structure constitutional isomer: connected differently Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Practice How many isomers ? C6H14

5 Ch.3 Organic Compounds: Alkanes and Cycloalkanes

- constitutional isomerism is not limited to alkanes

Different skeleton Butane Isobutane C4H10 (2-Methylpropane)

Different functional CH3CH2OH CH3OCH3 group Ethyl alcohol C2H6O

NH2 CH CH CH NH Different position of CH3CHCH3 3 2 2 2 functional group Ethyl alcohol Propylamine C3H9N Ch.3 Organic Compounds: Alkanes and Cycloalkanes

- different ways to represent n-butane (n= normal); n-C4H10

H H H H HCC C C H H3CCH2 CH2 CH3 CH3CH2CH2CH3 H H H H

HHHH H C C CH3(CH2)2CH3 C C H HHH H

these structures do not imply any specific geometry Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Names of straight chain alkanes: ending -ane

1 9 Nonane 2 Ethane 10 Decane 3 Propane 11 Undecane 4 Butane 12 Dodecane 5 Pentane 13 Tridecane 6 Hexane 20 Icosane 7 Heptane 21 Henicosane 8 Octane 30 Triacotane Ch.3 Organic Compounds: Alkanes and Cycloalkanes 3.3 Groups alkyl group: partial structure of alkane (-H); used for naming purpose

H C NH CH4 H3C H3C OH 3 2 Methane A Methyl alcohol Methyl amine

-CH CH CH CH -CH3 -CH2CH3 -CH2CH2CH3 2 2 2 3 Methyl (Me) Ethyl (Et) Propyl (Pr) Butyl (Bu)

-CH2CH2CH2CH2CH3 Pentyl, or Amyl Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Propyl (n-Pr) Isopropyl (i-Pr)

n-Butyl (n-Bu) sec-Butyl (s-Bu)

Isobutyl (i-Bu) tert-Butyl (t-Bu) Ch.3 Organic Compounds: Alkanes and Cycloalkanes four possible degrees of alkyl substitution for carbon

H H R C H R C H H R primary carbon (1o) secondary carbon (2o)

R R R C H RRC R R tertiary carbon (3o) quartenary carbon (4o)

R = a generalized alkyl group Ar = a generalized group Ch.3 Organic Compounds: Alkanes and Cycloalkanes

H H R R C OH R C OH R C OH H R R o primary alcohol (1o) secondary alcohol (2o) tertiary alcohol (3 )

CH 3 primary CH3CH2CHCH3

a tertiary secondary hydrogens

Ch.3 Organic Compounds: Alkanes and Cycloalkanes 3.4 Naming Alkanes

IUPAC: International Union of Pure and Applied Chemistry

Prefix Parent Suffix

Where are the ? How many ? What family? Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Step 1. Find the parent hydrocarbon.

a) the longest continuous chain of carbon atoms

hexane heptane Ch.3 Organic Compounds: Alkanes and Cycloalkanes

b) if two different chains of equal length are present ; choose the one with the larger number of branch points

two substituents one substituents Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Step 2. Number the atoms in the main chain. a) beginning at the end nearer the first branch point

1 6 3 2 4 5 7

heptane 7 2 4 NOT 6 4 3 1 Ch.3 Organic Compounds: Alkanes and Cycloalkanes b) if there is branching an equal distance away from both ends; begin the end nearer the second branch point

8 6 2 2 4 8 7 3 1 3 7 9 9 4 1 6 5 5

3,4,7 3,6,7

NOT Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Step 3. Identify and number the substituents.

a) assign a number to each according to its point of attachment to the main chain

8 6 2 7 3 1 3-ethyl 9 4 5 4-methyl 7-methyl a nonane Ch.3 Organic Compounds: Alkanes and Cycloalkanes b) If there are two substituents on the same carbon, give them both the same number.

6 3 1 2-methyl 4 2 5 4-methyl 4-ethyl a hexane Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Step 4. Write the name as a single word.

-use hyphens to seperate the different prefixes -use comma to seperate numbers -cite in alphabetical order - more than one identical substituents; di-, tri-, tetra-... (Don't use these prefixes for alphabetizing purposes)

3 3- Methylhexane

8 6 2 7 3 1 9 4 3-Ethyl-4,7-dimethylnonane 5 Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Me 3 2 3-Ethyl-2-methylheptane Et

4-Ethyl-3-methyloctane

4-Ethyl-2,4-dimethylheptane Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Step 5. Name a complex substituent just as though it were itself a compound.

8 1 3 7 10 2 4 6 5 9

2,3,6-trisubstituted decane Ch.3 Organic Compounds: Alkanes and Cycloalkanes

- begin numbering at the point of attachment

Molecule 2 3 1

2-methylpropyl group Ch.3 Organic Compounds: Alkanes and Cycloalkanes

The substituent is alphabetized according to the first letter of its complete name (including any numerical prefix) and is set off in parentheses.

8 1 3 7 10 2 4 6 5 9

2,3-Dimethyl-6-(2-methylpropyl)decane

6-Isobutyl-2,3-dimethyldecane Ch.3 Organic Compounds: Alkanes and Cycloalkanes

- alphabetizing the substituent: the first letter of the complete name (including any numerical prefix of the complex substituent)

8 1 3 5 7 2 4 6 9

1 5-(1,2-dimethylpropyl) 3 2 2-methyl

5-(1,2-Dimethylpropyl)-2-methylnonane Ch.3 Organic Compounds: Alkanes and Cycloalkanes Practice IUPAC Name

6-(1-ethylbutyl)

6

6-(1-Ethylbutyl)-3,5-dimethylundecane Ch.3 Organic Compounds: Alkanes and Cycloalkanes

common names: historical reason

three-carbon alkyl group

Isopropyl (i-Pr) four-carbon alkyl group

sec-Butyl (s-Bu) Isobutyl (i-Bu) tert-Butyl (t-Bu) Ch.3 Organic Compounds: Alkanes and Cycloalkanes

five-carbon alkyl group

Isopentyl or Neopentyl tert-Pentyl or isoamyl (i-amyl) tert-amyl (t-amyl) Ch.3 Organic Compounds: Alkanes and Cycloalkanes common name and IUPAC name, both are used

4-(1-Methylethyl)octane

or 4-Isopropyloctane

Caution iso, neo, cyclo are considered part of the alkyl-group for alphabetizing purposes but sec-, tert- are not. Ch.3 Organic Compounds: Alkanes and Cycloalkanes Practice IUPAC Name

2 7

2,7-Dimethylnonane Ch.3 Organic Compounds: Alkanes and Cycloalkanes Practice IUPAC Name

3-Isopropyl-2-methylhexane

2 3 3 Ch.3 Organic Compounds: Alkanes and Cycloalkanes 3.5 Properties of Alkanes

• alkanes are sometimes referred to as paraffins (meaning "slight affinity") ; little chemical affinity for other substances ; chemically inert to most laboratory reagents

• alkanes do react with oxygen, , and a few other substances under appropriate conditions

combustion

CH4 + 2 O2 CO2 + 2 H2O + 890 kJ/mol (213 kcal/mol) Ch.3 Organic Compounds: Alkanes and Cycloalkanes

photochemical chlorination

hν CH4 ++Cl2 CH3Cl HCl

Cl2 CH2Cl2 + HCl

Cl2 CHCl3 + HCl

Cl2 CCl4 + HCl Ch.3 Organic Compounds: Alkanes and Cycloalkanes

• b.p. or m.p. of alkane increases with molecular weight due to intermolecular dispersion forces (van der Waals forces) between .

; C1 -C4 (gas): C5 ~ (liquid) Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Dispersion forces (van der Waals forces) : operate only very small distances, arise because the electron distribution in alkane molecule, although uniform over the time, is likely to be nonuniform at any given instant. One side of a molecule may, by chance, have slightly excess of electrons relative to the opposite side, giving the molecule a temporary dipole moment. This temporary dipole in one molecule causes a nearby molecules to adopt a temporarily opposite dipole, with the result that a tiny electrical attraction is induced between the two. Temporary molecular dipoles have a fleeting existence and are constantly changing, but the cumulative effect of an enormous number of them produces attractive forces sufficient to cause a substance to remain in the liquid or solid state.

− − − δ δ+ δ δ+ δ δ+

attractive van der Waals force Ch.3 Organic Compounds: Alkanes and Cycloalkanes 3.6 Cycloalkanes • cycloalkanes or alicyclic compound

general formula: CnH2n

Cyclopropane

Cyclohexane

• b.p.of increases with molecular weight ; but, m.p. is affected by molecular weight and shape Ch.3 Organic Compounds: Alkanes and Cycloalkanes

O O H OH H H H CO2H H HO H OH

Chrysanthemic acid Prostaglandin E1 (PGE1) (insecticidal) (hormone which controls blood platelet aggregation, bronchial dilation, O inhibition of gastric secretion) OH O OH H

H H O Cortisone

Ch.3 Organic Compounds: Alkanes and Cycloalkanes 3.7 Naming Cycloalkanes

Step 1. Find the parent.

; if the number of carbons of ring ≥ the number of carbons in the substituent: name as cycloalkane

CH3 Methylcyclopentane

; if the number of carbons of ring < the number of carbons in the substituent: name as alkane

1-Cyclopropylbutane Ch.3 Organic Compounds: Alkanes and Cycloalkanes

Step 2. Number the substituents.

; for alkyl- and halo-substituted cycloalkanes: choose a point of attachment as C1 and number others so that the second substituent has as low a number as possible

1 1

3 5

1,3-Dimethylcyclohexane NOT Ch.3 Organic Compounds: Alkanes and Cycloalkanes

; if second point is same, choose lowest third or fourth Et Me Me

2 Et 1 Et 3 Et Me 4 Me Me 1 Me 6 Me Me 1 2 4

2-Ethyl-1,4-dimethylcycloheptane NOT Ch.3 Organic Compounds: Alkanes and Cycloalkanes

(a) When two or more different alkyl groups that could receive the same numbers of present, number them by alphabetical priority.

Et Et 1 2 Me Me 2 1 NOT

1-Ethyl-2-methylcyclopentane Ch.3 Organic Compounds: Alkanes and Cycloalkanes

(b) If are present, treat them exactly like alkyl groups

1 Me 2 Me

2 Br 1 Br

bromo > methyl

NOT 1-Bromo-2-methylcyclobutane Ch.3 Organic Compounds: Alkanes and Cycloalkanes Practice IUPAC Name

Br Br 1

Et Me Et3 5 Me

1-Bromo-3-ethyl-5-methylcyclohexane Ch.3 Organic Compounds: Alkanes and Cycloalkanes Practice IUPAC Name

1

(1-Methylpropyl)cyclobutane

sec-Butylcyclobutane Ch.3 Organic Compounds: Alkanes and Cycloalkanes Practice IUPAC Name

Cl Cl 1 Me Me 2 Et 3 Et

1-Chloro-3-ethyl-2-methylcyclopentane Ch.3 Organic Compounds: Alkanes and Cycloalkanes 3.8 Cis-Trans Isomerism in Cycloalkanes

• In many respects, the chemistry of cycloalkanes is like that of open- chain, acyclic alkanes; nonpolar, inert.

• But cycloalkanes are less flexible than acyclic alkanes. ; free rotation is possible around C-C bond in open-chain molecules (because σ-bond is cylindrically symmetrical)

H H H H C C rotate H H H H H C C HH H Ch.3 Organic Compounds: Alkanes and Cycloalkanes

• cycloalkanes (C3-C7) are severely restricted in their molecular motions • larger cycloalkanes have increasingly more rotational freedom

• very larger ring (C25 and up) are so floppy that they are nearly indistinguishable from open-chain alkanes.

H H H

H H H

No rotation is possible around the C-C bonds without breaking open the ring Ch.3 Organic Compounds: Alkanes and Cycloalkanes

• Cycloalkanes have two sides, a "top" side and a "bottom" side, leading to the possibility of isomerism in substituted cycloalkanes.

H3C CH3 H3C H H X H H H H CH3 H H

cis-1,2-Dimethylcyclopropane trans-1,2-Dimethylcyclopropane Ch.3 Organic Compounds: Alkanes and Cycloalkanes stereoisomer: atoms connected in the same order but differ in 3- dimensional orientation Constitutional isomers (different connections between atoms)

Stereoisomers (same connections but different 3-dimensional geometry)

H C CH H3C H 3 H 3 H

H H H CH3 H H

cis-1,2-Dimethylcyclopropane trans-1,2-Dimethylcyclopropane Ch.3 Organic Compounds: Alkanes and Cycloalkanes

• cis-trans isomer

CH 3 H3C CH3 H H H H H3C cis

Br H Br H H Et H Et

trans

HO OH OH H H HO cis Chemistry @ Work Gasoline from Petroleum

natural gas and petroleum: derived from the decomposition of plant and animal matter, primarily marine origin

- natural gas : methane (major), ethane, propane, butane, isobutane

- petroleum : complex of that must be refined into fractions before it can be used

refining by distillation of crude oil Chemistry @ Work Gasoline from Petroleum

Asphalt Lubricating oils, Heating oil

(C14 -C25) Petroleum

Kerosene

(C11 -C14)

Natural gas Straight-run gasoline (C5 -C11) (C1 -C4) Chemistry @ Work Gasoline from Petroleum

octane number: the measure by which its antiknock properties are judged

• straight-chain hydrocarbons are far more prone to induce engine knock than a highly branched compounds

CH3 CH3 H3C C CH2 C CH3 CH3CH2CH2CH2CH2CH2CH3 H CH3

Heptane Isooctane (octane number = 0) (octane number = 100)

bad fuel good fuel Chemistry @ Work Gasoline from Petroleum

• straight-run gasoline: a high percentage of unbranched alkanes, poor fuel

catalytic cracking: "cracking" high-boiling kerosene (C11-C14) into smaller molecules suitable for use in gasoline ; on silica-alumina catalyst, 400-500 oC

; major products are C3-C5 carbons which are then catalytically

recombined to C7-C10 alkanes