Systematic Organic Chemistry- Hydrocarbons Flashcards

0
Q

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

A

End on SIGMA bond

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1
Q

When is a covalent bond formed

A

When two half filled orbitals overlap

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2
Q

If orbital lie perpendicular to the bond and overlap they are

A

Side on PI bonds

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3
Q

The more multiple bonds the more

A

PI binds are present

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4
Q

What bond is stronger

A

Sigma bonds are stronger than PI bonds

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5
Q

What is hybridisation

A

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

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6
Q

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

A

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

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7
Q

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

A

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

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8
Q

Why are alkenes unreactive

A

Due to the non polar nature of bonds

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9
Q

Alkanes react with halogens in sunlight make halogenoalkanes

A

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

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10
Q

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

A

Chain reaction with 3 stages
Initiation
Propagation
Termination

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11
Q

What is homolytic fusion in initiation

A

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

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12
Q

What are radicals

A

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

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13
Q

What happen in propagation

A

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

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14
Q

Explain the termination step

A

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

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15
Q

How are alkenes prepared

A

Dehydration of alcohols

Base induced elimination of hydrogen halides from monohalogenoalkanes

16
Q

How is the dehydration of alcohols done

A

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

17
Q

What is base induced elimination of hydrogen halide from monohalogenoalkanes

A

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

18
Q

What reactions do alkenes undergo

A
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
19
Q

What is markovnikovs rule

A

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

20
Q

The mechanism for the halogen alkene reaction is

A
  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
21
Q

What is the process of hydrhalogenatio

A
  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)
22
Q

Explain acid catalysed hydration

A

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