You can start with 2- propanol, react it with sodium so that you get the alkoxide ion of the two reactant then follow it with an alkylhalide so that a nucleophilic substitution reaction can take place to form 2-methoxypropane. An alkylhalide to be used here be an alkyl of any of the halogen group or aklylsulfonate/aklylsulfate can be used also instead of alkylhalide
A reaction with alkyl halides in NaI with acetone is by the Sn2 mechanism. The rate for an Sn2 mechanism is directly proportional to the concentration of the nucleophile: rate = k[nucleophile][alkylhalide] If the iodine solution (the nucleophile) is half as concentrated, then the rate will also be halved. rate = k [nucleophile]/2 [alkyl halide]