halogenoalkanes Flashcards
(28 cards)
what is the general formula of a halogenoalkane?
CnH2n+1X
what bond do halogenoalkanes have?
C-X
why is the carbon hydrogen bond in a halogenoalkane polar?
● bond is polar as halogen is more electronegative than carbon
● Cδ+ - Xδ-
are halogenoalkanes soluble in water?
● C - X bond is polar
● but not polar enough to make haloalkanes soluble in water (polar solvent)
what do halogenoalkanes mix with?
haloalkanes mix with hydrocarbons (non-polar solvent)
what are halogenoalkanes used for?
dry cleaning fluids to remove oily stains
what intermolecular forces do halogenoalkanes have?
● vdws
● dipole dipole
what does the boiling point of a halogenoalkane depend on?
number of carbon and halogen atoms
explain the boiling point of halogenoalkanes
● boiling point increases with increased chain length
● boiling point increases down group 7
● due to increased vdw forces
why do halogenoalkanes have higher boiling points than alkanes of a similar length?
● higher relative molecular masses
● more polar
why do branched halogenoalkanes have lower points?
● as they have lower melting point
● less surface contact
● weaker vdws
what bond almost always breaks when haloalkanes react?
C-X bond
what are the 2 factors that determine how readily the C-X bond in halogenoalkanes breaks?
● Cδ+ - Xδ- bond polarity
● C-X bond enthalpy
why do haloalkanes get more reactive down the group?
● carbon - halogen bond has lower bond enthalpy as you go down group
● the lower the bond enthalpy, the more easily the bond is broken
● fluorine - smallest atom so shared pair of electrons in the C-F bond are strongly attracted to fluorine nucleus so very strong bond
● so iodoalkanes are most reactive
what is a nucleophile?
an electron pair donator
what are three common nucleophiles?
● hydroxide ion: OH-
● ammonia: NH3
● cyanide ion: CN-
what are three things a nucleophile could be?
● either a negatively charged ion or has atom with partially negative charge
● has lone pair of e- that it can use to form covalent bond: NH3
● has lone pair situated on the electronegative atom
what happens in a nucleophilic substitution reaction?
● a nucleophile will replace the halogen in a haloalkane
● electrons go to slightly positive carbon
what are the conditions when :OH- reacts with a halogenoalkane?
under reflux
what are the reagents when :OH- reacts with a halogenoalkane?
● halogenalkane +
● NaOH (aq) in ethanol
● KOH (aq) in ethanol
● ethanol used as solvent but water is also present
what are the products when :OH- reacts with a halogenoalkane?
● alcohol
● and halide ion
what are the conditions when :CN- reacts with a halogenoalkane?
under reflux
what are the reagents when :CN- reacts with a halogenoalkane?
● halogenoalkane +
● NaCN(aq) in ethanol
● KCN (aq) in ethanol
what are the products when :CN- reacts with a halogenoalkane and why is this useful?
● a nitrile
● product has more than one carbon than the reactant
