MCAT Study Guide Ochem Ch. 2 – Basics of Organic Chemistry 2017-08-15T06:45:05+00:00

I.          2.1 BACKGROUND AND INTRODUCTION (NOMENCLATURE)

A.     Basic nomenclature

Carbon Chain Prefixes and Alkane Names
# of C atoms in a row Prefix Alkane Name
1 Meth- CH4 Methane
2 Eth- CH3CH3 Ethane
3 Prop- CH3CH2CH3 Propane
4 But- CH3(CH2)2CH3 butane
5 Pent- CH3(CH2)3CH3 Pentane
6 Hex- CH3(CH2)4CH3 Hexane
7 Hept- CH3(CH2)5CH3 Heptane
8 Oct- CH3(CH2)6CH3 Octane
9 Non- CH3(CH2)7CH3 Nonane
10 Dec- CH3(CH2)8CH3 Decane

 

Nomenclature for Substituents

Nomenclature for Substituents
-CH3 Methyl
-CH2CH3 Ethyl
-CH2CH2CH3 Propyl
H3C-CH-CH3 Isopropyl
-CH2CH2CH2CH3 Butyl (or n-butyl)
CH3CHCH2CH3 sec-butyl
        CH3               ⃒-C-CH3⃒CH3 tert-butyl (or t-butyl)

B.     Common functional groups

II.          2.2 ABBREVIATED LINE STRUCTURE

 

III.          2.3 NOMENCLATURE OF ALKANES

A.     Rules

1.     Identify the longest chain of carbons (7 carbons, hept-)

2.     Identify substituents:  there are 3 methyl groups and 1 isopropyl goup

3.     Number the carbon chain so substituents have the lowest #

a)     2-methyl, 3-methyl, 3-methyl, 4-isopropyl

4.     Identical substituents are grouped together with the prefixes di-, tri-, etc to denote how many there are; numbers are separated by a comma

a)     2,3,3-trimethyl

5.     Alphabetize the substituents, ignoring prefixes (di-, iso-, etc); separate numbers from words by hyphen and numbers from numbers by comma

a)     2,3,3-trimethyl-4-isopropylheptane

 

IV.          2.4 NOMENCLATURE OF HALOALKANES

A.     Fluorine = fluoro-

B.     Chlorine = chloro-

C.    Bromine = bromo-

D.    Iodine = iodo-

V.          2.5 NOMENCLATURE OF ALCOHOLS

A.     Replace the “e” with “ol” in the last part of an alkane to name alcohol

1.     methane → methanol

B.     Position of the hydroxyl group

When the position of the hydroxyl group needs to be specified, the number is placed after the name of the longest carbon chain, but before the “ol” suffix, separated by hyphens

C.    Priorities are assigned to give the hydroxyl group the lowest number

 

VI.          2.6 Video notes

A.     Properties of Alkanes

1.     Branching and molecular weight:  melting point and boiling point

a)     Increase MW → increase MP and increase BP

b)     Increase branching → decrease MP and decrease BP

2.     Hydrogen bonding (H connected to F, O, or N)

a)     Increase H-bonding → increase MP and BP

3.     Reactivity vs stability:

Stability Reactivity
Carbocations(a C loses atom as well as e) 3º>2º>1º 1º>2º>3º
Radical(dangling bond – 1 e) 3º>2º>1º 1º>2º>3º
Carbanion(a C loses the atom, but not e) 1º>2º>3º 3º>2º>1º

4.     ACIDITY TRENDS → acids donate protons, accepts e-s, or decreases pH

a)     More stable of a conjugate base (usually due to resonance), the more acidic

b)     Strong acid has weak conjugate base (means base is not reactive b/c it is stable)

c)     Trends that increase acidity:

(1)   resonance increases acidity (ex, phenol)

(2)   + charge (OH, H2O, H3O+) the H3O+ is most acidic

(3)   Inductive effect – the more electronegative atoms near the acid, the more acid

(4)   → right on periodic table = increasing acidity

d)     Memorize:

Strong acids Strong bases
H2SO4 Group I and II hydroxides
HNO3 Na, K, Rb, Cs, Ca, Ba, Sr
HI
HBr
HCl
HClO4

 

e)     Weak acids, from strong to weak

(1)   Carboxylic acid >

(2)   Phenols >

(3)   Alcohols >

(4)   Aldehydes >

(5)   Ketones >

(6)   Alkynes >

(7)   Akenes >

(8)   Alkanes

MCAT Study Guide Ochem - Kim Matsumoto


More MCAT Study Guide Ochem