Introduction To Organic Chemistry

Question 1

Structural formula

Answer 1

(Formula showing how many atoms and their symbols are bonded to each carbon atom in a organic molecule )

• shows arrangement of atoms in a molecule

Eg. propane CH3HC=CH2

Question 2

Displayed formula

Answer 2

2D representation of organic molecule showing all atoms and all bonds

Question 3

Skeletal formula

Answer 3

Simplified displayed formula, all C & H atoms and C—H bonds removed

Question 4

Homologues series

Answer 4

Group of organic compounds having the same functional group, general formula and similar chemical properties

Question 5

Functional group

Answer 5

An atom or group of atoms in an organic molecule which determines the characteristic chemical reactions
Eg. -OH

Question 6

General formula

Answer 6

Formula representing homologous series of compounds
Eg. Alkanes : CnH2n+2

Question 7

Aliphatic compounds

Answer 7

Straight chain/ branched chain organic compounds or cyclic compounds.

Question 8

Structural isomers

Answer 8

Compounds with same molecular formula but different structural formulas

Question 9

Structural isomers types

Answer 9

1. Chain isomerism - main chain number of carbon changes
2. Position isomerism - position of the functional group changes
3. Functional group isomerism - same molecular formula but different functional groups

Question 10

Stereoisomers

Answer 10

Compounds whose molecules have the same atoms bonded to each other in the same way but different arrangement of atoms in space so molecules are non- superimposable

Question 11

Stereoisomers types

Answer 11

1. Geometrical - atoms can’t rotate around c=c double bond, rigid
   CIS - same groups on same side/ larger mr tgt (Z)
   TRANS- different sides(E)
2. Optical - mirror images of each other (enantiomers), have chiral carbon atom

Question 12

Enantiomers

Answer 12

A pair of optically active molecules whose mirror images are non- superimposable

Question 13

Chiral center

Answer 13

A carbon atom with four different atoms/groups attached
Allows optical isomers to exist

Question 14

Reaction mechanisms

Answer 14

steps that take place in course of overall reaction.
2 ways covalent bonds can break: Homolytic, Heterolytic.

Question 15

Homolytic fission

Answer 15

Covalent bond splits to form 2 free radicals
Electrons are equally shared from a pair in a covalent bond.
x ÷ y —-> x. + y.
The dot represents an unpaired electron

Question 16

Free radical reaction

Answer 16

3 step reaction that starts with the production of reactive atoms or molecules with an unpaired electron called INITIATION.
Second step regenerates free radicals called PROPAGATION. Then finishes with 2 free radical meeting to form a molecule called TERMINATION.

Question 17

Heterolytic fission

Answer 17

Covalent bond breaks to form 2 different ions.
Electrons are shared unequally from a pair in a covalent bond.
The more electronegative atom takes both electrons from a covalent bond.
Curly arrows used to show movement of electrons.
x ÷ ^y —-> x(+) + y (-)
Positively charged ion called a carbocation.

Question 18

Carbocation

Answer 18

An alkyl group with a single positive charge (fourth bond) on one of its carbon atoms.
3 types : Primary (1 alkyl group R), Secondary (2 alkyl groups 2R),Tertiary (3 alkyl groups 3R) which is most energetically stable and most likely to form in reaction mechanisms.

Carbon atom is electron deficient and the alkyl groups tend to be electron donating and they have a positive inductive effect.

Alkyl groups push electrons away from themselves and reduces the + charge of the carbocation and more stable so more alkyl groups equal more energetically stable.

They are electrophiles.

Question 19

Electrophiles

Answer 19

a species in organic chemistry that can act as an electron pair acceptor
Electron loving
Positively charged
Attacking agents
attack negative molecules
eg. H+, NO2+, CH3+, CH3CO+, Cl+/Br+/I+
and polar mol. eg H-Br, H2SO4

Question 20

Nucleophiles

Answer 20

species that can act as a donor of a pair of electrons
Nucleus loving
negatively charged
Attacking agent
attack positive molecules
eg. : OH-, NH3, H2O, CN-

Question 21

Types of organic reaction

Answer 21

1. Addition reactions : double bond broken, two molecules join to form 1 product. eg. alkene + X to alkane.
2. Elimination reactions: Removal of a small molecule from larger reactant molecule. 1 reactant, 2 products.
3. Condensation reactions: 2 organic molecules join together and eliminate a small molecule eg. water. addition followed by elimination.
4. Substitution reactions: replacement of an atom or a group of atoms by another. Replacement of functional groups.
   Eg. the free radical substitution of alkanes by chlorine in sunlight.

5.Oxidation reactions: Addition of oxygen, increase in oxidation number , removal of electrons or hydrogen. [O] represents oxygen atom from oxidizing agent.

6. Reduction reactions: removal of oxygen, decrease in oxidation number, addition of electrons. [H] represents hydrogen from reducing agent.

Question 22

Molecular formula

Answer 22

Gives actual number of atoms of element in a compound

Question 23

Empirical formula

Answer 23

Gives the simplest whole number ratio of atoms of each element in a compound

Question 24

Alkane general formula

Answer 24

CnH2n+2

BUT Cyclohexane is C6H12

Question 25

Alkene general formula

Answer 25

CnH2n

Question 26

Halogenoalkane Formula

Answer 26

CnH2n+1X

Functional group: C-X

Question 27

Alcohol Formula

Answer 27

CnH2n+2O

Functional group: R-OH

R is the carbon chain

Question 28

Aldehyde formula

Answer 28

CnH2nO

Functional group: R–CH=O

Question 29

Ketones

Answer 29

CnH2nO
same general formula as aldehyde.

Functional group: −C(=O)− carbonyl

Question 30

Carboxylic acid formula

Answer 30

CnH2nO2

Functional group: COOH

Question 31

Amine* formula

Answer 31

CnH2n+3N

Functional group: R-NH2