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CfE AH Chemistry > Unit Two > Flashcards

Unit Two Flashcards

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1
Q

What type of bonds are in Carbon double and triple bonds?

A

Carbon double bonds have one pi and one sigma bond.

Carbon triple bonds have 2 pi and 1 sigma bond.

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2
Q

Define Hybridisation

A

The process of mixing atomic orbitals within an atom to form a new set of degenerate hybrid orbitals.

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3
Q

Define Stereoisomerism

A

When the order of bonding in the atoms is the same but the arrangement of the atoms in space is different.

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4
Q

Why does geometric isomerism usually occur

A

Lack of rotation around carbon to carbon bond (This will either be a double bond or single bonds arranged in a cyclic alkane)

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5
Q

Why does optical isomerism occur?

A

Because of the different ways in which four groups can be arranged around a carbon atom.

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6
Q

What is the definition of a chiral molecule?

A

Carbon atom that has four different groups attached to it.

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7
Q

How can optical isomers be identified?

A

Pass plane polarised light through a solution of each isomer (both same concentration and volume). The plane polarised light will be rotated through a certain angle and when passed through the isomer it will be rotated by the same angle but in the opposite direction.

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8
Q

Define and give example of homolytic fission

A

This is when 2 species of the same charge are formed, an example this would be an initiation reaction to produce free radicals.

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9
Q

Define and give an example of heterolytic fission

A

This is when two species end up oppositely charged, this occurs when polar covalent bonds are broken and ions are formed.

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10
Q

What is a nucleophile?

A

A negatively charged species or species that are electron rich, these are attracted to positively charged centres.

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11
Q

What is an electrophile?

A

A positively charged species or species that are deficient in electrons, these are attracted to groups that can donate electrons.

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12
Q

What is Markovinikov’s rule?

A

The hydrogen always attaches to the carbon atom of the double bond that already has the greatest number of hydrogen atoms attached to it.

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13
Q

What does Sn1 and Sn2 stand for

A

Unimolecular nucleophilic substitution and bimolecular nucleophilic substitution.

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14
Q

How do you identify a Sn1 reaction?

A

The reaction rate does not depend on the concentration of the nucleophile as the nucleophile is not involved in the rate determining step.
It happens in tertiary haloalkanes.

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15
Q

How do you identify a Sn2 reaction?

A

Reaction rate is dependent on the concentration of the nucleophile.
It happens in primary and secondary haloalkanes.

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16
Q

How can alcohols be prepared?

A

Fermentation, Substitution of a haloalkane with sodium hydroxide and acid catalysed hydration of alkenes

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17
Q

How can you test for the presence of an alcohol?

A

Reaction with phosphorus pentachloride- HCl will form if present and this will result in the production of dense white fumes

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18
Q

What are the uses of alcohols?

A

Used as solvents in paints and dyestuffs, used as feedstocks to produce esters and polyesters. Polyhydric alcohols also have uses as glycerol is used in food and ethylene glycol is used as antifreeze.

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19
Q

How can ethers be formed?

A

Alcohol reaction with sodium or with haloalkanes

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20
Q

How can esters be produced more quickly than with an alcohol and carboxylic acid?

A

Alcohol and acid chloride, chlorine is a good leaving group

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21
Q

What are the main uses of ethers?

A

Their major use is as a solvent as they are non-polar so dissolve organic substances but not ionic substances, they have little reactivity with potential solutes and small molecules are volatile so are easily removed.

22
Q

How can aldehydes and ketones be reduced?

A

By reducing agent Lithium aluminium hydride (dissolved in ether)

23
Q

How can unknown aldehydes and ketones be identified?

A

Reaction with Brady’s reagent forms a precipitate in which melting point analysis can be done.

24
Q

How can amines be prepared?

A

Haloalkane reaction with ammonia (SN2). Or reduction of nitriles using aluminium hydride.

25
Q

What is the evidence that benzene has a sea of delocalised electrons and the double bonds are fluctuating?

A

Benzene does not decolourise bromine solution.
X-ray analysis shows all carbon to carbon bonds are equal in length
All carbon and hydrogen atoms lie in the same plane.

26
Q

What type of hybridisation takes place in benzene

A

sp2

27
Q

How can alkylbenzenes be produced?

A

Reacting a benzene ring with a haloalkane and aluminium chloride catalyst. The catalyst is needed to generate a positive electrophilic substituting reagent.

28
Q

When do pi bonds form?

A

When atomic orbitals lie perpendicular to the bond and overlap side on.

29
Q

When do sigma bonds form?

A

When orbitals overlap along the axis of the bond (end on).

30
Q

What type of molecule is benzene susceptible to attack from?

A

Electrophilic (molecules must be positive)

31
Q

How is nitrobenzene produced?

A

React benzene with excess concentrated Nitric and Sulphuric Acid.

32
Q

How is benzenesulphonic acid produced?

A

Heat benzene under reflux with excess concentrated sulphuric acid. (It is the SO3 molecules that is the electrophile).

33
Q

What is used as a baseline in NMR Spectroscopy

A

TMS/ tetramethylsilane

34
Q

What type of reaction takes place when a haloalkane is reacted with KOH in ethanol?

A

Elimination reaction to form an alkene

35
Q

Definition of an Agonist

A

Produces a response similar to the body’s natural active compound.

36
Q

Definition of an Antagonist

A

Produces no response but prevents the action of the body’s natural active compound.

37
Q

What is the definition of a chromophore?

A

Word used to describe the group of atoms within a molecule responsible for the absorption of light in the visible region of the electromagnetic spectrum.

38
Q

Explain in detail how colour arises in organic molecules

A
  • Most organic compounds appear colourless as the energy difference between the HOMO and the LUMO is relatively high and light is absorbed in the UV region of the spectrum.
  • Coloured organic compounds contain conjugated systems (series of alternating double and single bonds) resulting in delocalised electrons being spread over a few atoms.
  • This decreases the HOMO-LUMO energy gap resulting in light being absorbed in the visible region so the molecule is coloured.
  • Molecules appear the colour that is complementary to the colour of light they absorb.
  • The greater the degree of conjugation the smaller the HOMO-LUMO energy gap, the lower the absorbed energy and the more likely the molecule is to appear red.
39
Q

What is the definition of a pharmacophore?

A

The structural fragment of the molecule which gives it pharmacological activity and it is the part that binds to the receptor.

40
Q

What is the purpose of TMS in NMR spectroscopy?

A

It is used as a standard reference

41
Q

In a mass spectrometer what causes the separation of ions?

A

A magnetic field

42
Q

Why does an optical isomer of a drug not work as well?

A

The structure of the drug will fail to match the binding regions

43
Q

What do amines react with carboxylic acids to form?

A

Salts

44
Q

What do aldehydes and ketones form when reacted with hydrogen cyanide and what else is needed for this reaction to occur?

A

They form cyanohydrins and potassium cyanide is also needed for this reaction to occur.

45
Q

What can cyanohydrins undergo to form a hydroxycarboxylic acid?

A

Hydrolysis.

46
Q

How can carboxylic acids be prepared?

A

Hydrolysis of Nitriles or oxidation of a primary alcohol.

47
Q

What can two molecules of carboxylic acid form?

A

Anhydrides

48
Q

What gas is given off when lithium aluminium hydride reacts with water?

A

Hydrogen

49
Q

What is a benzene ring with NH2 group attached called?

A

Phenylamine

50
Q

What is a benzene ring with OH group attached called?

A

Phenol

CfE AH Chemistry (3 decks)

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