L12 - Organic Chemistry (2) Flashcards

1
Q

Define Aliphatic.

A

Compounds containing an open chain of carbon atoms.

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2
Q

Define Alicyclic.

A

Compounds containing a ring of saturated carbon atoms.

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3
Q

Define Aromatic.

A

Compounds containing a ring where all the atoms are unsaturated (and conjugated).

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4
Q

Define Heterocyclic.

A

Compounds containing a ring made up of Carbon and at least one other element, such as N, S or O.

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5
Q

What is significant about the functional groups in organic compounds?

A
  • Gives its characteristic chemical properties
  • Acts as the site of chemical reactivity
  • Serves as the basis of nomenclature
  • Classifies its family
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6
Q

What is the general structure of an Alkyl Halide?

A

R - X

halo

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7
Q

What is the general structure of an Alcohol?

A

R - O - H

hydroxy

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8
Q

What is the general structure of an Ether?

A

R - O R’

alkoxy

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9
Q

What is the general structure of an Amine?

A

R - N - H2

R - N - H, R’

R- N - R’, R’’

(amino)

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10
Q

What is the general structure of a Thiol?

A

R - S - H

thio / mercapto

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11
Q

What is the general structure of a Sulfide?

A

R - S - R’

alkathio

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12
Q

What is the general structure of an Aldehyde?

A

R - C = O, H

carbonyl

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13
Q

What is the general structure of a Ketone?

A

R - C = O, R

carbonyl

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14
Q

What is the general structure of a Carboxylic Acid?

A

R - C = O, OH

carboxyl

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15
Q

What is the general structure of an Ester?

A

R - C = O, OR’

alkyl

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16
Q

What is the general structure of an Amide?

A

R - C = O, N - R’, R’’

R - C = O, NH2

(H / Alkyl)

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17
Q

What is the general structure of an Acid Chloride?

A

R - C = O, Cl

COCl

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18
Q

Describe polyfunctional compounds.

A
  • Contain more than one functional group
  • Principle functional group determines the class
  • Secondary functional groups are treated as substituents
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19
Q

What is the order of preference for the principle group?

A

1) Carboxylic Acid
2) Ester
3) Acid Halide
4) Amide
5) Nitrile
6) Aldehyde
7) Ketone
8) Alcohol
9) Amine
10) Double Bond
11) Triple Bond
12) Hydrogen
13) Nitrogen

20
Q

Define Homologous Series.

A

Group of organic compounds with similar chemical properties, same functional group but differ by the length of the carbon chain; successive members differ by a CH2 unit.

21
Q

What are successive members of a homologous series called?

A

Homologues

22
Q

Describe the features of homologues.

A
  • Same general formula
  • Prepared by similar methods
  • Similar chemical properties
  • Gradual variation in physical properties with increasing molecular weight
23
Q

What does bonding in organic molecules use?

A

Linear combination of atomic orbitals

Orbitals combine to form hybrid atomic orbitals and molecular orbitals

24
Q

Describe the 2 atomic orbitals.

A

s-Orbital:

  • Spherical
  • Lower in energy than the other orbitals in the same shell

p-Orbital:

  • Dumbbell shape
  • Nodal plane passes through nucleus (no electron density at the node)
  • Higher in energy than s-orbital
  • 3 p-orbitals in the same shell
25
Q

Explain Hybridisation.

A

The idea that atomic orbitals fuse to form newly hybridised orbitals, which in turn, influences the molecular geometry and bonding properties.

26
Q

Explain Hybridisation, with reference to Carbon.

A

1) Carbon has 2 unpaired electrons, yet it forms 4 bonds

2) One of the 2s electrons can be promoted into the vacant p orbital in 2p
- Requires energy input
- Favourable because of decreased electron-electron repulsion

3) The 2s and 2p orbitals now mix to form various hybrid atomic orbitals

27
Q

Describe SP3 Hybridisation.

A
  • All 4 atomic orbitals (2s, 2 px, 2 py, 2 pz) combine to give the same number of new hybrid atomic orbitals
  • All 4 sp3 orbitals are equivalent with the same energy (degenerate)
  • Orbitals point towards the corners of a tetrahedron
  • Overlap produces sigma bonds
28
Q

What is SP3 Hybridisation used for bonding in?

A

Used for bonding in saturated compounds

29
Q

Describe SP2 Hybridisation.

A
  • The s and two p orbitals (2 px, 2 py) combine to give three new hybrid atomic orbitals
  • The 3rd p orbital (2 pz) remains unchanged
  • SP2 orbitals point towards the corners of a triangle
  • Used for sigma bonding
  • The p orbital is perpendicular to them
  • Used for pi bonding
30
Q

What is SP2 Hybridisation used for bonding in?

A

Used for bonding in alkenes, carbonyls and aromatic rings

31
Q

Describe SP Hybridisation.

A
  • The s and one p orbital (2 px) combine to give two new hybrid atomic orbitals
  • The other 2 p orbitals (2 py, 2pz) remain unchanged
  • SP orbitals are at 180° to one another (linear molecule)
  • Used for sigma bonding
  • The 2 p orbitals are perpendicular to them
  • Used for pi bonding
32
Q

What is SP Hybridisation used for bonding in?

A

Used for bonding in alkynes and nitriles

33
Q

Describe the properties of hybrid orbitals.

A
  • Hold electrons closer to the nucleus
  • Bond becomes shorter, and therefore stronger
  • More directional, so they have effective bonding interactions
  • The more s-character in an orbital, the lower the energy (leads to increased stability of an electron in that orbital)
34
Q

The overlap of orbitals forms two types of bonds depending on the ________ of the overlap.

A

The overlap of orbitals forms two types of bonds depending on the geometry of the overlap.

35
Q

How are sigma (σ) bonds formed?

A

By direct overlap

36
Q

Describe sigma (σ) bonds.

A
  • Electron density is along the line of the bond
  • Symmetric with relation to rotation about the bond
  • Bond may be formed between s-s, p-p, s-p or hybridised orbitals
  • The bonding molecular orbital is lower in energy than the original atomic orbitals
37
Q

Describe sigma (σ) bonding in methane.

A

1) Four sp3 hybrid orbitals form a tetrahedron
2) Add four hydrogen atoms
3) Combine sp3 and 1s
4) Each molecular orbital is the same and has σ symmetry

38
Q

Describe sigma (σ) bonding in ethane.

A

1) Each carbon uses three sp3 orbitals to bond to hydrogens

2) Remaining sp3 orbital on each carbon overlaps to form a carbon-carbon bond

39
Q

How are pi (π) bonds formed?

A

By the parallel overlap of p orbitals

40
Q

Describe pi (π) bonds.

A
  • Electron density is above and below the plane of the bond
  • Form after sigma bonds
  • Higher in energy than sigma bonds, therefore weaker and more easily broken
41
Q

Describe the nature of bonding in a double bond.

A

(2 pairs of shared electrons)

  • Consists of 1 sigma bond and 1 pi bond
42
Q

Describe the nature of bonding in a triple bond.

A

(3 pairs of shared electrons)

  • Consists of 1 sigma bond and 2 pi bonds
43
Q

Describe the bonding in benzene.

A
  • π electrons are delocalised around the ring, above and below the plane
  • All bond lengths are identical (between single and double bonds)
44
Q

Describe the different bonding types in relation to bond length and bond strength.

A

Bond Strength (Strongest to Weakest):

  • Triple Bond
  • Double Bond
  • Single Bond

Bond Length (Longest to Shortest):

  • Single Bond
  • Double Bond
  • Triple Bond

The stronger the bond, the shorter the bond length.

45
Q

What type of hybridisation do the different bonds undergo?

A
  • Single Bond: sp3
  • Double Bond: sp2
  • Triple Bond: sp