introduction to organic chemistry

Question 1

what is a functional group and examples (alkane and alkene)

Answer 1

particular atoms or a group of atoms within an organic molecule, that define the physical properties and chemistry of that compound
alkane: NA
alkene: C=C

Question 2

what are the degrees of substitutions and draw them out

Answer 2

primary, secondary, tertiary

Question 3

what is the difference between empirical formula, molecular formula, structural formula, displayed formula, skeletal formula and stereochemical formula

Answer 3

empirical: simplest ratio (CH2O)

molecular: actual number of atoms (C3H6O3)

structural formula: shows how the atoms of a molecule are joined together with minimal detail (CH3CH(OH)CO2H)

displayed formula: detailed structure of molecule showing the relative placing of atoms and all the bonds between them (drawing)

skeletal formula: no hydrogen and hydrogen bonds, no carbon atoms

stereochemical formula: shows the 3D spatial arrangement of bonds, solid wedges indicate bonds pointing out of the plane of the paper towards you, dashed wedges indicate bonds pointing into the plane of the paper away from you and lines indicate bonds in the plane of the paper.

Question 4

Nomenclature: stem from 1 to 10

Answer 4

meth, eth, prop, but, pent, hex, hept, oct, non, dec

Question 5

Nomenclature: type of carbon-carbon bonds present in the longest carbon chain

Answer 5

-an: all C-C
-en: one C=C
-dien: two C=C
-trien: three C=C
-yn: one C≡C

Question 6

different types of organic reactions

Answer 6

substitution
addition
elimination
condensation
hydrolysis
oxidation
reduction

Question 7

what is substitution

Answer 7

when one atom or group of atoms replaces another atom or group in a molecule

Question 8

what is elimination

Answer 8

when a C=C is formed with the removal of a molecule

Question 8

what is addition

Answer 8

when an organic molecule (usually C=C) reacts with another molecule to give only one product. pi bond of double bond breaks to form two new sigma bonds

Question 8

what is condensation

Answer 8

when two molecules come together to form a bigger molecule, with the elimination of a small molecule like water

Question 9

what is hydrolysis

Answer 9

when a molecule is split into two by the action of water, often catalysed by dilute acids or dilute alkalis

Question 9

what is oxidation

Answer 9

when O atoms are added to the molecule / when H atoms are removed from the molecule

Question 9

what is reduction

Answer 9

when O atoms are removed from the molecule / when H atoms are added to the molecule

Question 10

electrophile definition (lewis acids)

Answer 10

a species that accepts an electron pair to form a covalent bond in a reaction. it is electron-deficient due to having:
- a positively-charged center
- an induced or permanent partial positive charge (dipole molecules)

Question 11

nucleophile definition (lewis bases)

Answer 11

a species that donates an electron pair to form a covalent bond in a reaction. it is electron-rich and possesses electrons that can be shared, such as
- long pairs of electrons
- pi bond (ethene)

Question 12

factors affecting organic reactivities

Answer 12

inductive effect
delocalisation
steric effect (not an electronic effect)

Question 13

what is the inductive effect

Answer 13

occus via sigma bonds and due to the difference in electronegativity between atoms in covalent bonds. gets weaker with distance

Question 14

what is delocalisation

Answer 14

occurs due to 3 or more p orbitals overlapping, forming a pi electron cloud. it is independent of distance. the pi electrons in the two C=C bonds are delocalised throughout the pi electron cloud and not just localised at their respective double bonds. the C-C bond has partial double character and is somewhat stronger and shorter than a C-C single bond.

Question 15

what is the steric effect

Answer 15

the larger the groups and the greater the number of groups crowding around the site of reaction, the greater the steric hindrance.

the steric effect is a result from the repulsion between electron clouds of groups of substituents, depending on their size and number. molecules with bulky substituents crowded around their reactive sites would hinder the approach of the other reactant for an effective collision.

Question 16

what is homolytic fission

Answer 16

breaking of a covalent bond where the bonding pair of electrons are given equally to each atom. results in the formation of free radicals

Question 17

what is heterolytic fission

Answer 17

breaking of a covalent bond where both bonding electrons are given one of the atoms, usually the more electronegative one. results in the formation of ions

Question 18

what are carbocations?

Answer 18

species containing a positively-charged carbo atom, which has only six electrons in its outer shell. (due to a more electronegative element, like Cl)

Question 19

what are carbanions?

Answer 19

species containing negatively charged carbon atom, which has a full octet of electrons in its outer shell.