Synthesis Flashcards
1
Q
What happens when an organic reaction takes place
A
When an organic reaction takes place, bonds in the reactant molecules are broken down and bonds in the product molecules are made
2
Q
What is the process bond breaking known as
A
The process of bond breaking is known as bond fission
3
Q
What are the two types of bond fission
A
There are two types of bond fission homolytic and hetrolytic
4
Q
Homolytic fission :
A
- 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
5
Q
Why are products of homolytic fission unsuitable for organic synthesis
A
Reactions involving homolytic fission tend to result in the formation of very complex mixtures of products making them unsuitable for organic synthesis
6
Q
Hetrolytic fission
A
- results in the formation of two oppositely charged ions
- occurs when one atom retains both electrons from the sigma covalent bond and the bond breaks unevenly
- normally occurs when polar covalent bonds are broken
7
Q
Why are hetrolytic reactions better suited for organic synthesis
A
Reactions involving hetrolytic fission tend to result in far fewer products than reactions involving homolytic fission and so are better suited for organic synthesis
8
Q
What does a single headed arrow indicate
A
- a single headed arrow indicates the moevement of a single electron
9
Q
What does a double headed arrow indicate
A
A double headed arrow indicates the moevement of an electron pair
10
Q
What does the tail of the arrow show
A
The tail of the arrow shows the source of the electron
11
Q
What does the head of the arrow indicate
A
The head of the arrow indicates the destination of the electron
12
Q
What do two single headed arrows starting at the middle of a covalent bond indicate
A
Two - single headed arrows starting at the middle of a covalent bond indicate homolytic bond fission is occuring
13
Q
What does a double headed arrow starting at the middle of a covalent bond indicate
A
A double headed arrow starting at the middle of a covalent bond indicates hetrolytic bond fission is occuring
14
Q
What does an arrow drawn with the head pointing to the space between two atoms indicate
A
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
15
Q
How are attacking groups classifies in reactions involving heterolytic bond fission
A
In reactions involving heterolytic bond fission attacking groups are classified as nucleophiles or electrophiles
16
Q
What are nucleophiles
A
Nucleophiles are negatively charged ions or neutral molecules that are electron rich, such as Cl-, Br-, CN-, NH3 and H20
17
Q
What are nucleophiles attracted towards
A
Attracted towards atoms bearing a partial (δ+) or full positive charge
18
Q
What are nucleophiles capable of
A
Capable of donating an electron pair to form a new covalent bond
19
Q
Electrophiles are
A
Positively charged ions or neutral molecules that are electron deficient such as H+, NO2, and SO3
20
Q
What are electrophiles attracted towards
A
Attracted towards atoms bearing a partial (δ-) or full negative charge
21
Q
What are electrophiles capable of
A
Capable of accepting an electron pair to form a new covalent bond
22
Q
Alkanes
A
- alkanes are the simplest homologous series
- alkanes contain c-c single bonds and are saturated
- the general formula is CnH2n+2
- the names of alkanes always end in ANE
23
Q
Alkenes
A
- alkenes are another homologous series of hydrocarbons
- alkenes contain at least one c=c double bond and are unsaturated
- general formula is CnH2n
- the name of alkenes sometimes contain a number, this number indicates the position of the double bond
24
Q
Types of branches
A
Methyl branch - one carbon atom - CH3
Ethyl branch - two carbon atoms - C2H5
Propyl branch - three carbon atoms - C3H7
25
If a side chain occurs more than once
di (2 branches)
tri (3 branches)
tetra (4 branches)
26
Branched alkane
1 - identify the longest carbon chain, name alkane with this number of carbon atoms
2 - identify branch name and name it according to the number of carbon atoms in the branch
3- number branch so it has the lowest of two possible numbers
27
Branched Alkenes
- position of double bond must be Identified
- number showing position placed before -ene
- the position of the double bond is more important than the position of the branch
28
Naming alcohols
The basic rules of naming apply: the position of the hydroxyl group is indicated before the “ol” part
29
General formula for carboxylic acids
Carboxylic acids
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How to name carboxylic acid
The naming of carboxylic acids is similar to alkanes however the ending is replaced with “oic acid”
31
Addition reaction
Something unsaturated turns saturated
H2C=CH2 + H2 ——> C2H6
32
Hydration (A type of addition reaction)
Adding water to form often an alcohol
H2C=CH2 +H20 ———> C2H5OH
33
Elimination (opposite to addition)
C2H5OH ——> H2C=CH2 + H2O
34
Condensation (an example of this is esterification)
When you take two molecules and join them together in the process you eliminate a small molecule
Alcohol ROH. + Carboxylic acid RCOOH <=> RO-C=O-R ( this is meant to be an ester link)
+ H2O
35
Hydrolysis
Use of water to split up a larger molecule
R- ESTER LINK + H2O ———> ROH + RCOOH
36
Substitution (electrophilic)
Benzene ring - H. + HNO3 ——> Benzene ring - NO2
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Substitution (nucleophilic)
H3C-CL + KOH ——> H3C-OH + KCL
38
Reduction
A decrease in the OH ratio
RCOOH ——> RCOH
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Oxidation
An increase in the OH ratio
ROH ——> RCOOH
40
What is an ester
An ester is a molecule containing an ester link -COO
41
Which reactions are esters formed by
Esters are formed by a condensation reaction between an alcohol and a carboxylic acid with concentrated sulphuric acid as a catalyst
42
What is the equation for an ester
Alcohol + carboxylic acid ——> ester + water
43
How to name an ester
- first part comes from the parent alcohol
- second part comes from the parent carboxylic acid
44
What is the small molecule eliminates when an ester link is formed
When an ester link is formed by the reaction between a hydroxyl group and a carboxyl group the small molecule eliminated is water
45
What happens in a hydrolysis reaction
In a hydrolysis reaction a molecule reacts with water to break down into smaller molecule
46
What is produced when esters are hydrolysed
Esters can be hydrolysed to produce an alcohol and carboxylic acid
47
What is the equation of breaking down (hydrolysis) of an ester
Ester + water ——> acid and alcohol
48
What are aldehyde and ketones
Aldehydes and ketones are molecules containing a carbonyl functional group C=O
49
What can primary alcohols oxidise to
Primary alcohol ——> aldehyde ——> carboxylic acid
50
What can secondary alcohols oxidise to
Secondary alcohol ——> ketone
51
What can a tertiary alcohol oxidise to
Tertiary alcohol ——> does not oxidise
52
How to name an aldehyde
Step 1: Name the longest chain that contains the carbonyl group
Step 2: Number chain with carbonyl
= 1
Step 3: Name the branches and number according to step 2
Step 4: If multiple of the same branch use di-, tri- etc, if different types of branch then name alphabetically
53
How to name a ketone
Step 1: Name the longest chain that contains the carbonyl group
Step 2: Number chain with from end closes to carbonyl
Step 3: Name the branches and number according to step 2
Step 4; If multiple of the same branch use di-, tri- etc, if different types of branch then name alphabetically
54
What are alcohols
Alcohols are substituted alkanes in which one or more of the hydrogen atoms is replicated with a hydroxyl functional group
55
Alcohols can be prepared from
- haloalkanes by substitution
- alkenes by acid-catalysed hydration (addition)
- aldehydes and ketones by reduction using a reducing agent such as lithium aluminium hydride
56
Reactions of alcohols include (1)
- dehydration to form alkenes using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid
57
Reactions of alcohols include (2)
- 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
58
Reaction of alcohols include (3)
- 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
59
Reactions of alcohols include (4)
- formation of esters by reaction with carboxylic acids using concentrated sulfuric acid or concentrated phosphoric acid as a catalyst
60
Reactions of alcohols include (4)
Formation of esters by reaction with acid chlorides (-c=o-cl) this gives a faster reaction than reaction with carboxylic acids and no catalyst is needed
61
What effect do hydroxyl groups have on alcohols
Hydroxyl groups make alcohols polar which gives rise to hydrogen bonding, hydrogen bonding can be used to explain the properties of alcohols including boiling points melting points, viscosity and solubility or miscibility in water
62
What are ethers
Ethers can be regarded as substituted alkanes in which a hydrogen atom is replaced with an alkoxy functional group, –OR, and have the general structure R' – O – R'', where R' and R'' are alkyl groups.
63
How are ethers named
Ethers are named as substituted alkanes. The alkoxy group is named by adding the
ending ‘oxy’ to the alkyl substituent, and this prefixes the name of the longest carbon
chain.
64
What type of boiling point do ethers have
Due to the lack of hydrogen bonding between ether molecules they have lower boiling points than the corresponding isomeric alcohols
65
How can ethers be prepared
Ethers can be prepared in a nucleophilic substitution reaction by reaction a monohaloalkane with an alkoxide
66
Why are ethers commonly used as solvents
Ethers are commonly used as solvents since they are relatively inert chemically and will dissolve many organic compounds.
67
What happens to solubility of ethers in water in relation to size
Methoxymethane and methoxyethane are soluble in water. Larger ethers are insoluble in water due to their increased molecular size.
68
What are monohaloalkanes
Monohaloalkanes (alkyl halides) are substituted alkanes in which one of the hydrogen atoms is replaced with a halogen atom
69
What do monohaloalkanes contain
They contain only one halogen atom and are saturated meaning they only have single sigma bonds
70
How can monohaloalkanes be classified
Can be classified as primary, secondary or tertiary according to the number of alkyl
groups attached to the carbon atom containing the halogen atom
71
A primary monohaloalkane
The carbon which contains the halogen atom is bonded to ONE other carbon atom (alkyl)
72
A secondary monohaloalkane
The carbon which contains the halogen is bonded to TWO other carbon atoms
73
A tertiary monohaloalkane
The carbon which contains the halogen is bonded to THREE other carbon atoms
74
How can we imagine each R group in monohaloalkanes
If we imagine each R group (alkyl/carbon) attached as a “bouncer” we can identify if the molecule is easy to attack
Harder to attack as more bouncers (1 R group compared to 3 R groups)
75
What is the least and most stable cation
Least stable cation - primary
Most stable cation - tertiary
76
Alkenes can be prepared by:
- dehydration of alcohols using aluminium oxide, concentrated sulfuric acid or concentrated phosphoric acid
- base-induced elimination of hydrogen halides from monohaloalkanes
77
Alkenes take part in 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
78
What are the alkoxy (-OR) group
Methoxy CH3O-
Ethoxy C2H5O-
Propoxy C3H7O-
79
How to name ethers
The longest alkane chain gives the parent name and the shorter alkoxy group prefixes this
80
What is the most significant feature of a halogenoalkane
The most significant feature of a halogenaolkane is the production of a dipole and in particular a positively charged carbon
The carbon is now vulnerable to attack by a number of different nucleophiles leading to nucleophilic substitution
81
What does markovnikov’s rule state
Markovnikov’s rule states that 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. Markovnikov’s rule can be used to predict major and minor products formed during the reaction of a hydrogen halide or water with alkenes
82
How do monohaloalkanes take part in elimination reactions
take part in elimination reactions to form alkenes using a strong base, such as
potassium or sodium hydroxide in ethanol
83
How do monohaloalkanes take part in nucleophilic substitution reactions
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
84
What reactions can a monohaloalkane take part in
A monohaloalkane can take part in nucleophilic substitution reactions by one of two
different mechanisms.
85
What is SN1 nucleophilic substitution
SN1 is 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.
86
What is SN2 substitution
SN2 is 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.
87
Steric hindrance
- with one methyl and two hydrogen atoms there is still room for the nucleophile to attach to the carbonium ion
- with three methyl groups and no hydrogen atoms there is no room for the nucleophile to attach to the carbonium ion
88
Inductive effect
89
Carboxylic acids can be prepared by
- 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
90
Reactions of carboxylic acids include
- 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
91
What are amines
Amines are organic derivatives of ammonia in which one or more hydrogen atoms of
ammonia has been replaced by an alkyl group.
92
How can amines be classified as
Amines can be classified as primary, secondary or tertiary according to the number of alkyl groups attached to the nitrogen atom.
93
How soluble are amine molecules
Primary, secondary and tertiary amine molecules can hydrogen-bond with water molecules, thus explaining the appreciable solubility of the shorter chain length amines in water.
94
What amines have hydrogen bonding
Primary and secondary amines, but not tertiary amines, display hydrogen bonding. As a result, primary and secondary amines have higher boiling points than isomeric tertiary amines.
95
How do amines like ammonia dissociate
Amines like ammonia are weak bases and dissociate to a slight extent in aqueous solution.The nitrogen atom has a lone pair of electrons which can accept a proton from water, producing hydroxide ions.
96
What is benzene
Benzene (C6H6) is the simplest member of the class of aromatic hydrocarbons
97
What is the stability of the benzene ring due to
The stability of the benzene ring is due to the delocalisation of electrons in the conjugated dydtem
98
What is the explanation of why benzene ring does not take part in addition reactions
The presence of delocalised electrons explains why the benzene ring does not take part in addition reactions
99
What is a benzene ring in which one hydrogen atom has been substituted
A benzene ring in which one hydrogen atom has been substituted by another group is known as the phenyl group. The phenyl group has the formula -C6H5
100
What is the bonding in benzene ring
It has both sigma and pi bonds so is sp2 hybridises due to alternating c=c bonds
101
Nitration of benzene ring
- nitration using concentrated sulfuric acid and concentrated nitric acid
Benzene ring —> conc sulfuric acid nitric acid -> benzene ring -NO2
102
Sulfonation of benzene ring
- Sulfonation using concentrated sulfuric acid
Benzene ring —-> sulfuric acid ——> benzene ring - SO3H
103
Alkylation of benzene ring
Alkylation by reaction of a haloalkane using aluminium chloride
Check flashcard
104
Halogenation of benzene ring
- halogenation by reaction of a halogen using aluminium chloride or iron (III) chloride chlorination and aluminium bromide or iron (III) bromide for bromination
Check flashcards
105
Homolytic jab chem
Homolytic fission has a covalent bond splitting with one electrons going to either end of the bond to form free radicals
106
Heterolytic fission jab chem
Heterolytic fission has a covalent bond splitting with both electrons going to one end of the bond to form a positive ion and negative ion.
107
Neutralisation
Acid and base reaction to form water and salt
108
Oxidising agent - acidified permanganate
Purple ——> colourless
109
Oxidising agent - acidified dichromate
Orange ——> green
110
Oxidising agent - hot copper (II) oxide
Black ——> brown
111
Carboxylic acids react with metals or bases to form salts.
2CH3COOH + Mg ——> Mg(CH3COO)2. + H2
CH3COOH + NaOH ——> NaCH3COO. + H2O
HCOOH + CaO. ——> Ca(HCOO)2. + H2O
2C2H5COOH. +K2CO3. ——> 2KC2H5COO. + H2O + CO2
