Systematic Organic Chemistry- Hydrocarbons

Question 0

If the overlap of a covalent bond is along the axis it is called a

Answer 0

End on SIGMA bond

Question 1

When is a covalent bond formed

Answer 1

When two half filled orbitals overlap

Question 2

If orbital lie perpendicular to the bond and overlap they are

Answer 2

Side on PI bonds

Question 3

The more multiple bonds the more

Answer 3

PI binds are present

Question 4

What bond is stronger

Answer 4

Sigma bonds are stronger than PI bonds

Question 5

What is hybridisation

Answer 5

Process of mixing atomic orbitals on an atom to generate a set of new atomic orbitals called HYBRID ORBITALS

Question 6

Bonding in alkanes with 3 2P orbitals and 1 2s

Answer 6

Form to four degenerate hybrid orbitals
Sp^3 hybrids and point to corners of tetrahedron to minimise repulsion
Later develop sigma bonds

Question 7

In alkenes when 2s and 2 of the 3 2p orbitals

Answer 7

Form sp^2 hybrid orbitals which adopt a trigonal planar arrangement
Later forms sigma bonds and PI bonds

Question 8

Why are alkenes unreactive

Answer 8

Due to the non polar nature of bonds

Question 9

Alkanes react with halogens in sunlight make halogenoalkanes

Answer 9

Example of substitution- reaction in which atom or group of atoms in a molecule replaced by another group of atoms

Question 10

What kind if reaction is a substitution between an alkali and halogen

Answer 10

Chain reaction with 3 stages
Initiation
Propagation
Termination

Question 11

What is homolytic fusion in initiation

Answer 11

Using UV light to provide energy to break bonds and split mols into atoms
Occurs with little or no polarity in bonds

Question 12

What are radicals

Answer 12

E ample chlorine atoms
Are atoms or groups of atoms with unpaired electrons
Extremely unstable and highly reactive
Produced by initiation step

Question 13

What happen in propagation

Answer 13

Radicals attack other reactant mol removing hydrogen to for other radicals of different kinds
Propagating or sustaining chain reaction
Radical represented by dot

Question 14

Explain the termination step

Answer 14

As the number of radicals build up collisions occur and stable mols are produced
Radicals used up and not produced
Chain reaction to an end

Question 15

How are alkenes prepared

Answer 15

Dehydration of alcohols

Base induced elimination of hydrogen halides from monohalogenoalkanes

Question 16

How is the dehydration of alcohols done

Answer 16

Alcohol vapour passed over hot aluminium oxide or alcohol treated with conc phosphoric acid
Elimination reaction

Question 17

What is base induced elimination of hydrogen halide from monohalogenoalkanes

Answer 17

Heating monohalogenoalkanes under reflux with ethanolic potassium hydroxide (dissolved in ethanol NOT water)
Can result in formation of two alkenes

Question 18

What reactions do alkenes undergo

Answer 18

Addition reaction to form Alkanes
Halogens dihaloalksnes
Hydrogen halides to form monohalogenoalkanes 
Water 
To form alcohol
Add hydrogen = hydrogenation 
Halogen= halogenation 
Hydrogen halide = hydro halogenation
Water = hydration catalysed by an acid

Question 19

What is markovnikovs rule

Answer 19

States the main products of the reaction between the unsymmetrical alkene and water/hydrogen halide where hydrogen atoms add to the carbons of the double bond with larger num of hydrogen atoms already attached

Question 20

The mechanism for the halogen alkene reaction is

Answer 20

1. = bromine mol approaches double bond and becomes polarised
   Electron rich double bond pushes electrons in bromine mol towards bromine atom which is remote gaining a slightly negative charge and positive charge between two bromine atoms
   Cyclic ion intermediate formed song with bromide ion (electrophile = electron pair acceptor ) bond in bromide breaks said to have undergone heterocyclic fission
2. = the br- ion attacked he intermediate ion from opposite side acting as a nucleophile (an electron pair donor) seeking out the central positive ion

Question 21

What is the process of hydrhalogenatio

Answer 21

1. = H-br mol already polarised as H already slightly positive so it attacks the double bond forming an intermediate called carbocation
   Bond in H-Br mol is breaking heterolytically and a bromide ion is formed as well
2. = bromide ion attacks carbocation intermediate
   Attacking from either side
   A halogen actsbunsymmetricalky with an alkene (two possible products)

Question 22

Explain acid catalysed hydration

Answer 22

H ion from acid acts as an electrophile and attacks electron rich double bond to form carbocation
Then carbocation undergoes a nucleophile attack from water mol
New alcohol very strong readily looses an proton
Hydrogen released at the end