How can you obtain iodoethane from ethanol when no other iodine containing reagent except NaI is available in the laboratory?
Ethanol is treated with red phosphorous and bromine mixture and the product formed will be bromoethane. The bromoethane so formed is then treated with Nal to give iodoethane.
$$\begin{gathered} \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OH} \xrightarrow{\mathrm{Red} \mathrm{P} / \mathrm{Br}_2} \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{Br} \\ \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{Br} \xrightarrow{\mathrm{Nal}} \mathrm{CH}_3 \mathrm{CH}_2 \mathrm{I}+\mathrm{NaBr} \end{gathered}$$
This reaction is known as Finkelstein reaction.
Cyanide ion acts as an ambident nucleophile. From which end it acts as a stronger nucleophile in aqueous medium? Give reason for your answer.
Cyanide ion $(\bar{:}C \equiv \mathrm{~N}$ ) is an ambident nucleophile because it can react either through carbon or through nitrogen. Since, $\mathrm{C}-\mathrm{C}$ bond is stronger than $\mathrm{C}-\mathrm{N}$ bond so, cyanide ion will mainly attack through carbon to form alkyl cyanide.
Match the the compounds given in Column I with the effect given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | Chloramphenicol | 1. | Malaria |
| B. | Thyroxine | 2. | Anaesthetic |
| C. | Chloroquine | 3. | Typhoid fever |
| D. | Chloroform | 4. | Goiter |
| 5. | Blood substituent |
A. $\rightarrow(3)$ B. $\rightarrow$ (4) C. $\rightarrow$ (1) D. $\rightarrow(2)$
A. Chloramphenicol is a broadspectrum antibiotic. It is used in the treatment of typhoid fever.
B. Thyroxine is a hormone secreated by thyroid gland. Execessive secretion of thyroxine in the body is known as hyperthyroidism. Most patient with hyper thyroidism have an enlarged thyroid gland i.e., goitre.
C. Chloroquine prevents the development of malaria parasite plasmodium vivax in the blood.
D. IUPAC name of chloroform is trichloromethane with formula $\mathrm{CHCl}_3$. It is a colourless, volatile, sweet-smelling liquid. Its vapours depresses the central nervous system and used as an anaesthetic.
Match the items of Column I and Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. | $\mathrm{S_N 1}$ reaction | 1. | vic-dibromides |
| B. | Chemicals in fire extinguisher | 2. | gem-dihalides |
| C. | Bromination of alkenes | 3. | Racemisation |
| D. | Alkylidene halides | 4. | Saytzeff rule |
| E. | Elimination of HX from alkylhalide | 5. | Chlorobromocarbons |
A. $\rightarrow(3)$ B. $\rightarrow$ (5) C. $\rightarrow$ (1) D. $\rightarrow$ (2) E. $\rightarrow$ (4)
A. A mixture containing two enantiomers in equal proportions will have zero optical rotation, such a mixture is known as racemic mixture. The process of conversion of enantiomer into a racemic mixture is known as racemisation. If an alkyl halide follows $\mathrm{S}_{\mathrm{N}} 1$ mechanism then racemisation takes place while if it follows $\mathrm{S}_{\mathrm{N}} 2$ mechanism than inversion takes places.
B. Chlorobromocarbons are used in fire extinguishers.
C. In vicinal dihalides, halogen atoms are present on the adjacent carbon atom. Bromination of alkenes will give vicinal dihalides.
D. Alkylidene halides are named as gem-dihalides. In gem-dihalides halogen atoms are present on same carbon atom.
E. Elimination of HX from alkylhalide follows Saytzeff rule. This rule states that "in dehydrohalogenation reactions, the preferred product is that alkene which has the greater number of alkyl groups attached to the doubly bonded carbon atoms".
Match the structures of compounds given in Column I with the classes of compounds given in Column II.
| Column I | Column II | ||
|---|---|---|---|
| A. |  |
1. | Aryl halide |
| B. | $\mathrm{CH}_2=\mathrm{CH}-\mathrm{CH}_2-X$ | 2. | Alkyl halide |
| C. |  |
3. | Vinyl halide |
| D. | $\mathrm{CH}_2=\mathrm{CH}-X$ | 4. | Allyl halide |
A. $\rightarrow(2)$ B. $\rightarrow(4)$ C. $\rightarrow$ (1) D. $\rightarrow(3)$
A. In alkyl halide, halogen atom is bonded to $s p^3$ hybridised carbon atom, which may be further bonded to one, two or three alkyl group, i.e., $\mathrm{CH}_3 \mathrm{CH}(\mathrm{X})-\mathrm{CH}_3$
B. Allyl halides are the compounds in which the halogen atom is bonded to $s p^3$ hybridised carbon atom next to carbon-carbon double bond. i.e., $\mathrm{CH}_{2-}=\mathrm{CH}-\mathrm{CH}_2-X$
C. Aryl halides are the compounds in which the halogen atom is bonded to $s p^2$ hybridised carbon atom of an aromatic ring, i.e., $\mathrm{C}_6 \mathrm{H}_5 \mathrm{X}$
D. Vinyl halides are the compounds in which the halogen atom is bonded to an $s p^2$ hybridised carbon atom of a carbon-carbon double bond, i.e., $\mathrm{CH}_2=\mathrm{CH}-X$