halogen derivatives Flashcards
what is the general formula of monohalogenoalkanes, aryl halides, acid halides
CnH(2n+1) X, Ar-X, O=C-Ar
/
X
explain the boiling point of halogen derivatives
CH3I>CH3BR>CH3CL>CH3F>CH4
1. As size of halogen atoms increases, the number of electrons in the molecules increases and electron cloud of the molecule becomes increasingly more polarisable. The instantaneous dipole- induced dipole interactions between the moleules to be stronger. hence, more energy is needed to overcome.
- As number of carbon atoms increases, nuber of electrons in molecule increases and the eectron cloud of the moelcule becomes more polarisable. the instantaneous dipole-induced dipole interactions become stronger. hence, more energy needed to overcome
why are halogenoalkanes more soluble in org solvents
though halogenoalkanes are polar, they are insoluble in water.energy released from formation of new interactions are insufficient to compensate the energy needed to overcome original interactions
what is the solubility of halogenoalkanes?
halogenoalkanes with one CL atom less dense than water. all bromoalkanes an iodoalkanes are denser than water. polyhalogens are denser than water
reaction and R&C for alkanes? (to form halogenoalkane)
free radical substitution. uv light and excess br2
reaction and R&C for alkenes? (to form halogenoalkanes)
electrophilic addition. room temperature and HX / X2
reaction and 4 types of R&C for alcohols? (to form halogenoalkanes) what is formed besides halogenoalkanes?
nucleophilic substitution.
- room temperature and HX. water is formed too
- room temperature and PX3. H3PO3 is formed too
- room temperature and PCL5. POCL3 and HCL are formed too
- room temperature and SOCL2. SO2 and HCL are formed too
reaction and R&C for arenes? (to form aryl halides)
electrophilic substitution. br2 and anhydrous albr3
explain the order of reactivity of alkyl halides, R-F, R-CL, R-BR, R-I
reactivity decreases from R-I> R-BR> R-CL> R-F.
this is because C-X bond becomes stronger from C-I to C-F
explain the reactivity of aryl halides. are they more reactive that akyl halides?
aryl halides less reactive than akyl halides.
1. a lone pair in the p orital of the halogen atom is delocalised into the pi electron cloud of the benzene ring, this strengthnes the C-X bond. this C-X bond is said to have partial double bond character.
2. interaction of the p orbital of the halogen atom with the pi electron cloud of the benzene ring causes a drift of electron density from X towards electron deficient carbon atom. this reduces polarity of the bond
3. the electron rich ring hindersnucleophilic attack
names the types of reactions under nucleophilic substitutionof akyl halides
- reaction with OH
- reaction with CN-
- reaction with ethanolic ammonia
4.reaction with ethanolic amines
how to form alcohol from alkyl halide? R&C, end product？
nucleophilic substitution. NaOH (aq) or KOH (aq), heat under reflux. endproduct is R-OH and X-
how to form nitrile from alkyl halide? r&c, product?
nucleophilic substitution. ethanolic NaCN or ethanolic KCN, heat under reflux. R-CN (nitrile) and X-
r&c of nitrile synthesis?
- nitrile to AMINE
Ni, heat , add H2 to nitrile
OR LiAlH4 in dry ether, add 【H】 - nitrile to carboxylic acid
dilute H2SO4, heat under reflux, add H+ and H2O to nitrile. carboxylic acid RCOOH and NH4+ formed - nitrile to carboxylate
dilute NaOH, heat under reflux, add OH- and H2O to nitrile. carboxylate RCOO- and NH3 formed
how to form amine from alkyl halide? r&c and product?
nucleophilic substitution. add NH3 to alkyl halide. ethanolic medium, heat in a sealed tube. amine and HX produced
