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AH Chemistry - Unit 3 > Synthesis > Flashcards

Synthesis Flashcards

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1
Q

What happens when an organic reaction takes place?

A

Bonds in the reactant molecules are broken and bonds in the product molecules are made.

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2
Q

What is the process of bond breaking known as?

A

Bond fission

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3
Q

What are the two types of bond fission?

A

Homolytic and heterolytic

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4
Q

What are three facts about homolytic fission?

A
  • It results in the formation of two neutral radicals
  • Occurs when each atom retains one electron from the sigma covalent bond and the bond breaks evenly
  • Normally occurs when non-polar covalent bonds are broken
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5
Q

What does heterolytic fission result from? And what happens in Heterolytic fission?

A

Results in the formation of two oppositely charged ions occurs when one atom retains both electrons from the covalent bond and the bond breaks unevenly normally occurs when polar covalent bonds are broken

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6
Q

Reactions involving heterolytic fission tend to result in far fewer? This makes them better suited for?

A

Products than reactions involving homolytic fission, and so are better suited for organic synthesis.

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7
Q

The movement of electrons during bond fission and bond making can be represented using curly arrow notation where…

A
  • a single-headed arrow indicates the movement of a single electron
  • a double-headed arrow indicates the movement of an electron pair
  • the tail of the arrow shows the source of the electron(s)
  • the head of the arrow indicates the destination of the electron(s)
  • two single-headed arrows starting at the middle of a covalent bond indicate homolytic bond fission is occurring
  • a double-headed arrow starting at the middle of a covalent bond indicates heterolytic bond fission is occurring
  • an arrow drawn with the head pointing to the space between two atoms indicates that a covalent bond will be formed between those two atoms
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8
Q

In reactions involving heterolytic bond fission, attacking groups are classified as?

A

Nucleophiles or electrophiles.

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9
Q

Nucleophiles are? Give some examples of molecules that are nucleophiles?

A

Negatively charged ions or neutral molecules that are electron rich, such as Cl , Br , OH , CN , NH and H2O attracted towards atoms bearing a partial (𝝈)+ or full positive charge capable of donating an electron pair to form a new covalent bond

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10
Q

Electrophiles are?

A

Positively charged ions or neutral molecules that are electron deficient, such as H + , NO2 + 3 and SO attracted towards atoms bearing a partial (𝝈)− or full negative charge capable of accepting an electron pair to form a new covalent bond

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11
Q

A carbocation is a carbon with a?

A

Positive charge

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12
Q

Carbocations have varying? What does this depend on?

A

Stability depending on which groups are attached and are important intermediates in organic synthesis.

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13
Q

A carbanion is a carbon with a?

A

Negative charge

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14
Q

Carbanions are also… in?

A

Intermediates in reaction mechanisms.

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15
Q

The following reaction types can be identified from a chemical equation…

A

Substitution addition elimination condensation hydrolysis oxidation reduction neutralisation

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16
Q

Synthetic routes can be?

A

Devised, with no more than three steps, from a given reactant to a final product.

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17
Q

The possible reactions of a particular molecule can be deduced by looking at the?

A

Structural formula.

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18
Q

In a skeletal structural formula what is not shown?

A

Neither the carbon atoms, nor any hydrogens attached to the carbon atoms, are shown.

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19
Q

The presence of a carbon atom is implied by a?

A

‘kink’ in the carbon backbone, and at the end of a line.

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20
Q

What are Haloalkanes (alkyl halides)?

A

Substituted alkanes in which one or more of the hydrogen atoms is replaced with a halogen atom.

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21
Q

Give 2 pieces of information on Monohaloalkanes…

A
  • contain only one halogen atom can be classified as primary, secondary or tertiary according to the number of alkyl groups attached to the carbon atom containing the halogen atom
  • take part in elimination reactions to form alkenes using a strong base, such as potassium or sodium hydroxide in ethanol take part in nucleophilic substitution reactions with: — aqueous alkalis to form alcohols — alcoholic alkoxides to form ethers — ethanolic cyanide to form nitriles (chain length increased by one carbon atom) that can be hydrolysed to carboxylic acids
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22
Q

A monohaloalkane can take part in what kind of reaction?

A

Nucleophilic substitution reactions by one of two different mechanisms.

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23
Q

SN1 is what sort of reaction? What occurs in this reaction?

A

Nucleophilic substitution reaction with one species in the rate determining step and occurs in a minimum of two steps via a trigonal planar carbocation intermediate.

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24
Q

SN2 is what sort of reaction? What occurs during this reaction?

A

A nucleophilic substitution reaction with two species in the rate determining step and occurs in a single step via a single five-centred, trigonal bipyramidal transition state.

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25
Q

The reaction mechanisms for SN1 and SN2 reactions can be represented using?

A

Curly arrows

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26
Q

The mechanism that will be preferred for a given haloalkane can be explained by?

A

Steric hindrance and the inductive stabilisation of the carbocation intermediate

27
Q

Alcohols are?

A

Substituted alkanes in which one or more of the hydrogen atoms is replaced with a hydroxyl functional group, –OH group.

28
Q

Alcohols can be prepared from? By what reaction type?

A

Haloalkanes by substitution alkenes by acid-catalysed hydration (addition) aldehydes and ketones by reduction using a reducing agent such as lithium aluminium hydride

29
Q

Reactions of alcohols include…

A

Dehydration to form alkenes using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid oxidation of primary alcohols to form aldehydes and then carboxylic acids and secondary alcohols to form ketones, using acidified permanganate, acidified dichromate or hot copper(II) oxide formation of alcoholic alkoxides by reaction with some reactive metals such as potassium or sodium, which can then be reacted with monohaloalkanes to form ethers formation of esters by reaction with carboxylic acids using concentrated sulfuric acid or concentrated phosphoric acid as a catalyst formation of esters by reaction with acid chlorides — this gives a faster reaction than reaction with carboxylic acids, and no catalyst is needed

30
Q

Hydroxyl groups make alcohols… which gives rise to?

A

Polar, which gives rise to hydrogen bonding.

31
Q

Hydrogen bonding can be used to explain the properties of alcohols including….

A

melting points, viscosity and solubility or miscibility in water.

32
Q

Ethers can be regarded as substituted alkanes in which a hydrogen atom is replaced with an?

A

alkoxy functional group, –OR, and have the general structure R’ – O – R’’, where R’ and R’’ are alkyl groups.

33
Q

Ethers are named as?

A

Substituted alkanes.

34
Q

The alkoxy group is named by?

A

Adding the ending ‘oxy’ to the alkyl substituent, and this prefixes the name of the longest carbon chain.

35
Q

Ethers can be prepared in a nucleophilic substitution reaction by?

A

Reacting a monohaloalkane with an alkoxide.

36
Q

Due to the lack of hydrogen bonding between ether molecules, they have?

A

Lower boiling points than the corresponding isomeric alcohols.

37
Q

Methoxymethane and methoxyethane are soluble in?

A

Water

38
Q

Larger ethers are insoluble in water due to?

A

Their increased molecular size.

39
Q

Ethers are commonly used as? Why is this?

A

Solvents since they are relatively inert chemically and will dissolve many organic compounds.

40
Q

Alkenes can be prepared by?

A

Dehydration of alcohols using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid base-induced elimination of hydrogen halides from monohaloalkanes

41
Q

Alkenes take part in what sort of reactions? What does this form in the presence of…

A

Electrophilic addition reactions with: hydrogen to form alkanes in the presence of a catalyst halogens to form dihaloalkanes hydrogen halides to form monohaloalkanes water using an acid catalyst to form alcohols

42
Q

Markovnikov’s rule states that?

A

When a hydrogen halide or water is added to an unsymmetrical alkene, the hydrogen atom becomes attached to the carbon with the most hydrogen atoms attached to it already.

43
Q

Markovnikov’s rule can be used to predict?

A

Major and minor products formed during the reaction of a hydrogen halide or water with alkenes.

44
Q

The reaction mechanisms for the addition of a hydrogen halide and the acid-catalysed addition of water can be represented using? And showing…

A

Curly arrows and showing the intermediate carbocation.

45
Q

The reaction mechanism for the addition of a halogen can be represented using? And showing?

A

Curly arrows and showing the cyclic ion intermediate.

46
Q

Carboxylic acids can be prepared by?

A

Oxidising primary alcohols using acidified permanganate, acidified dichromate and hot copper(II) oxide oxidising aldehydes using acidified permanganate, acidified dichromate, Fehling’s solution and Tollens’ reagent hydrolysing nitriles, esters or amides

47
Q

Reactions of carboxylic acids include?

A

Formation of salts by reactions with metals or bases condensation reactions with alcohols to form esters in the presence of concentrated sulfuric or concentrated phosphoric acid reaction with amines to form alkylammonium salts that form amides when heated reduction with lithium aluminium hydride to form primary alcohols

48
Q

Amines are?

A

Organic derivatives of ammonia in which one or more hydrogen atoms of ammonia has been replaced by an alkyl group.

49
Q

Amines can be classified as?

A

Primary, secondary or tertiary according to the number of alkyl groups attached to the nitrogen atom.

50
Q

Amines react with acids to form?

A

Salts

51
Q

Primary and secondary amines, but not tertiary amines, display?

A

Hydrogen bonding

52
Q

Why do primary and secondary amines have higher boiling points than isomeric tertiary amines?

A

Because they have hydrogen bonding

53
Q

Primary, secondary and tertiary amine molecules can ….. with water molecules, what does this explain?

A

Hydrogen-bond. The appreciable solubility of the shorter chain length amines in water

54
Q

Amines like ammonia are weak… what do they do?

A

Bases and dissociate to a slight extent in aqueous solution.

55
Q

The nitrogen atom has a lone pair of electrons which can? producing?

A

Accept a proton from water, producing hydroxide ions.

56
Q

Benzene (C6H6) is the simplest member of the class of?

A

Aromatic hydrocarbons.

57
Q

The stability of the benzene ring is due to the?

A

Delocalisation of electrons in the conjugated system.

58
Q

The presence of delocalised electrons explains why the benzene ring does not take part in?

A

Addition reactions.

59
Q

Bonding in benzene can be described in terms of?

A

sp2 hybridisation, sigma and pi bonds, and electron delocalisation

60
Q

A benzene ring in which one hydrogen atom has been substituted by another group is known as the?

A

Phenyl group

61
Q

The phenyl group has the formula?

A

–C6H5.

62
Q

Benzene rings can take part in what kind if reaction?

A

Electrophilic substitution reactions.

63
Q

Reactions at benzene rings include?

A

Halogenation by reaction of a halogen using aluminium chloride or iron(III) chloride for chlorination and aluminium bromide or iron(III) bromide for bromination alkylation by reaction of a haloalkane using aluminium chloride nitration using concentrated sulfuric acid and concentrated nitric acid sulfonation using concentrated sulfuric acid

AH Chemistry - Unit 3 (5 decks)

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