IB Docs (2) Team MC test: Electrophilic addition & electrophilic substitution reactions
Multiple choice test on 20.1(2 & 3) Electrophilic addition & electrophilic substitution reactions
Use the following 'quiz' to test your knowledge and understanding of this sub-topic. You will need access to a periodic table (Section 6 of the IB data booklet). Note that this quiz covers both electrophilic addition and electrophilic substitution reactions.
If you get an answer wrong, read through the explanation carefully to learn from your mistakes.
What does a 'fish-hook' represent when used in organic reaction mechanisms?
Fish-hooks are used to show the movement of a single electron in organic reaction mechanisms. For example, they can be used to show radical formation when a bond breaks homolytically during free radical substitution reactions
Which reagents can be used to make 1-bromopropane directly as the major product ?
Both bromine and hydrogen bromide can add to propene but the products will be 1,2-dibromopropane and 2-bromopropane respectively. Propane can react with bromine in ultraviolet light to form 1-bromopropane (as well as 2-bromopropane) by a free radical mechanism.
What is the major product that will be formed when 2-methylpropene reacts with iodine monochloride?
Iodine monochloride is polar, Iδ+− Clδ− as iodine is less electronegative than chlorine. According to Markovnikov's rule the δ+ iodine atom will add to the carbon atom that already contains the most hydrogen atoms bonded to it. This is because the intermediate will be a tertiary carbocation, which is more stable than the alternative primary carbocation that would be formed if it added to the other carbon atom.
What will be the major organic intermediate formed during the reaction of pent-1-ene with hydrogen bromide?
Secondary carbocations are more stable than primary carbocations. The intermediate formed will be CH3CH2CH2C+HCH3.
Which is the correct order of increasing stability (least stable first)?
Due to the positive inductive effect of the R− groups, which stabilizes the carbocation, the order is primary < secondary < tertiary.
What type of organic compound will be formed when 2-methylbut-1-ene is reacted with hydrogen bromide and the major product of that reaction is then warmed with dilute sodium hydroxide solution, NaOH(aq).
Bromine will add to form 2-bromo-2-methylbutane, 
.
2-methylbutane will then react with the hydroxide ion to form 2-methylbutan-2-ol, 
.
Which will give a major and a minor organic product when they undergo an addition reaction with hydrogen iodide?
With 2-methylbut-2-ene the major product will be 2-iodo-2-methyl-butane and the minor product will be 2-methyl-3-iodobutane. The other three alkenes are symmetrical (have the same groups attached to the carbon atoms of the C=C double bond) so will only give one product.
When a mixture of concentrated sulfuric and nitric acid is reacted with benzene at 50 oC the organic product formed is nitrobenzene.
What is the initial role of the sulfuric acid?
It protonates the nitric acid to give H2NO3+ which then dissociates to give the electrophile, NO2+ and water.
When a mixture of concentrated sulfuric and nitric acid is reacted with benzene at 50 oC the organic product formed is nitrobenzene.
What is the initial role of the nitric acid?
It functions as a Lewis base (and a Brønsted–Lowry base) with sulfuric acid, HNO3 + H2SO4 → H2NO3+ + HSO4−. The protonated acid then breaks down to produce the nitryl cation (also called the nitronium ion), NO2+, which acts as the electrophile.
Using your knowledge of organic chemistry what will be the organic product when benzene reacts with chloromethane in the presence of aluminium chloride?
Although this reaction (known as alkylation) is not on the IB syllabus you should be able to deduce that as aluminium chloride is electron deficient it will act as a Lewis acid attracting an electron pair from CH3δ+−Clδ−. The chlorine atom bonds to AlCl3 to form AlCl4− leaving CH3+ which can act as the electrophile. Benzene will undergo electrophilic substitution with CH3+ to produce methylbenzene.
Twitter
Facebook
LinkedIn