Haloalkanes – Alkyl Halides – problem list
Classify the type of halide (primary, secondary, tertiary, allylic or benzyl) from the following list and draw the carbocation(s) obtained from each.
Classify the type of halide (primary, secondary, tertiary, allylic or benzyl) from the following list and draw the carbocation(s) obtained from each of them.
(a) draw the structures of the following compounds:
- 1-chlorobutane (I)
- 2-chloro-2-methyl-propane (II)
- 3-chloroprop-1-ene (III)
b) Order these compounds from highest to lowest reactivity for the SN1 reaction.
(a) Draw the structures of the following compounds:
- 2-chloro-2-methylpropane (I)
- 1-chloropropane (II)
- 2-chloropropane (III)
- chloromethane (IV)
(b) Order these compounds from highest to lowest reactivity for reaction SN2.
Describe the mechanism of the reaction of formation of 2-methoxy-2-methylpropane from 2-chloro-2-methylpropane when the latter is heated in methanol.
Draw the structure of the reaction product of methyl bromide with the following substances:
- Hydrogen sulfide
- Bisulfide ion
- Sodium cyanide
What nucleophiles will be necessary to obtain the following compounds from CH3-CH2-CH2-CH2-CH2-Br ?
2-bromo-2-methylpropane when dissolved in acetic acid is transformed into 2-methylbutan-2-yl acetate.
a) Define the type of reaction.
b) Justify why if sodium acetate is added to the reaction medium no appreciable variation in the rate of reaction is observed.
When tert-butyl bromide is treated with an aqueous solution of silver nitrate, the formation of a precipitate is observed. Propose a reaction mechanism compatible with this fact.
Indicate which molecule of the following pairs reacts most rapidly with sodium azide in acetone:
- 2-bromopropane vs. 1-bromopentane
- 2-bromopropane vs. 2-chloropropane
- 1-bromopentane vs. 1-bromocyclohexane
1-bromopropane reacts with sodium methoxide in methanol to give methyl propyl ether in 90% yield, whereas 1-bromo-2-methylpropane under the same conditions gives isobutyl methyl ether only in 40% yield. Justify the result.
The substitution reaction between 1-iodopropane and cyanide ion is of type SN2. Draw the reaction profile and explain what happens when the concentration of cyanide ion is halved in the reaction medium.
Of the following pairs of reactants, indicate which would be a better nucleophile:
a) Cl– / I–; b) CH3S– / CH3O–; c) H2O / HO–; d) CH3O– / F–
1-iodo-2-methylbutane reacts independently with the following reagents:
I) NaOH / MeOH
II) NaOH / DMSO
III) NaSH / MeOH
IV) NaSH / DMSO
a) Draw the product obtained in each case.
b) Deduce which will be the fastest reaction in the series.
Which type of reaction (SN1 or SN2) is most likely to occur in the following transformations?
Complete the following scheme:
Rank the following halides in increasing order of reactivity for an SN2 type reaction and against the same nucleophile.
Rank the following substrates in decreasing order of solvolysis rate.
Propose a mechanism that justifies the following transformation:
When 4-chloro-butanol is treated with a solution of NaOH, THF is obtained. Justify the result.
The following molecules can give under the appropriate conditions elimination reactions.
a) Mark with a dashed circle the positions of the α-hydrogens with respect to the leaving group.
b) Draw the structure of all the alkenes obtained in each case, indicating the one formed in the highest proportion for the usual conditions of the reaction.
Complete the following reactions and derive the rate equation for each.
Draw the structure of the compounds obtained under the appropriate conditions when the following compounds are treated independently with NaCN in acetone and methanol.
The reaction of (S)-3-bromo-3-methylhexane with methanol leads to a mixture of products.
a) Indicate how the concentration of methanol affects the final result.
b) Properly represent the structures of the compounds obtained.
Choose the appropriate reagent to perform the following transformations.
Select the mechanism (SN1, SN2, E1, E2, NO React) under the following reaction conditions:
(1R,2R)-1-bromo-2-ethylcyclohexane and (1S,2R)-1-bromo-2-ethylcyclohexane are treated independently with alcoholic potash in ethanol. Indicate in each case the result of the reaction.
Which of these compounds generates a single alkene when treated with sodium methoxide?
Complete these transformations (A-F) and explain in a reasoned way which will be the most likely mechanism in each case.
Deduce which reactions will be faster from the following pairs:
When (R)-3-bromo-2,3-dimethylpentane is dissolved in an equimolecular mixture of water and methanol, four products different from the starting one are obtained after a time. Justify this result.
Choose the most favorable conditions for the following transformations to occur:
Applying Zaitsev’s rule deduce which is the most stable alkene.
Draw the structure of the major compound obtained by treating the following molecules with sodium ethoxide in ethanol.
Justify the higher reaction rate of I (cis) versus II (trans) in the E2 reaction.
1-Iodo-2-methylpropane is treated with sodium metal to give 2,5-dimethylhexane and as by-products 2-methylpropane and 2-methylpropene. Justify the results.
Complete the following scheme:
Complete the following scheme:
Arrange the following halides in increasing order of reactivity in an SN2 reaction against the same nucleophile.
Choose the nucleophiles and solvents you consider most suitable, from those listed below, to perform the following transformations:
Rank in increasing order of solvolysis rate the following substrates.
Complete the following reactions and deduce the most likely type of reaction (E1, E2, SN1, SN2).
Justify why 3-bromopentane exhibits a higher nucleophilic substitution reaction rate than 1-bromo-2,2-dimethylpentane, despite being a secondary halide.
State what would be the major product of E2 elimination when the following products are treated with KOH in ethanol:
When E2 elimination of the following products occurs:
one of them performs it 50 times faster than the other. which of the two isomers is and why?
What will be the result of treating the following haloalkanes with NaOEt/EtOH or with t-BuOK/t-BuOH?
- a) Chloromethane
- b) 1-Bromopentane
- c) 2-Bromopentane
- d) 1-chloro-1-methylcyclohexane
- e) 1-Bromoethylcyclopentane
- f) (2R,3R)-2-chloro-3-ethylhexane
- g) (2R,3S)-2-chloro-3-ethylhexane
- h) (2S,3R)-2-chloro-3-ethylhexane
Explain why the following experimental results:
Describe what are all the possible products of the acetolysis (CH3COOH) of 1-iodo-1-methylcyclohexane and 2-iodo-1-methylcyclohexane.
Describe the result of treating (3S,4S)-3-bromo-4-methylhexane and (3S,4R)-3-bromo-4-methylhexane independently with:
(a) alcoholic potash; (b) potassium tert-butoxide; (c) sodium azide; (d) tri-n-butyltin hydride.
Considering Zaitsev’s rule, select the most stable alkene.
Choose the starting product (I-X) and the most suitable reaction conditions for obtaining the following molecules (a-f) by elimination reactions.
Independently treat the relative cis- and trans-stereochemistry isomers of 1-chloro-2-methylcyclohexane with alcoholic potash. Analyze the outcome of these reactions employing the Newman projection for each case.
Draw the structure of the starting products that you consider most suitable for preparing the following hydrocarbons by Corey-House synthesis, such that the carbon skeleton marked with thick stroke is incorporated into the final product from a single product.
What product is obtained from the following reactions?
Select the starting brominated derivatives (I-XI) needed to obtain, by Corey-House synthesis, the alkanes (a-d), where the C-C bond formation points are indicated.