Essay about Relative Reactivity of Alkyl Halides

Relative Reactivity of Alkyl Halides


Nucleophilic replacement of alkyl halides can proceed by simply two different mechanisms – the SN2 and the SN1. The purpose of the experiment was going to identify the effects that the alkyl group and the halide-leaving group have for the rates of SN1 reactions, and the effect that the solvent has on the rates of SN1 and SN2 reactions. The SN1 mechanism is actually a two-step nucleophilic substitution, or perhaps unimolecular displacement. In the very first step of the system, the carbon-halogen bond fails and the halide ion giving group leaves in a slower, rate-determining step to form a carbocation intermediate. The carbocation intermediate is then right away detained by weak nucleophile in a fast, second stage to give the item. A solution of ethanol which includes silver nitrate may be added provided the weak nucleophile – the alcohol. If an SN1 effect occurs, the alkyl halide will dissociate to form a carbocation, which will after that react with all the ethanol to create an ether. Since there isn't a strong nucleophile present, the cleavage with the carbon-halogen bond is encouraged by formation and precipitation of silver bromide. The halide ion is going to combine with a silver ion from the silver nitrate to form a silver halide precipitate, that will advise which a reaction features occurred. & AgBr + NO3-

Figure 1: The SN1 mechanism of 2-bromo-2-methylpropane and silver nitrate. The nucleophile might have been ethanol while the silver precious metal nitrate might have disassociated to form a silver halide precipitate. The greater stable the carbocation, the quicker the response. Therefore , SN1 reactions desire tertiary substrates most, and then secondary, not only that primary. � Because the power of the nucleophile is unimportant, an ionizing solvent is required. Water is the foremost solvent, followed by methanol, ethanol, propanol, not only that acetone. In experiment two, the tertiary 2-bromo-2-methylpropane was the most popular reactant and then the extra 2-bromobutane, the principal 1-bromobutane, plus the primary 1-chlorobutane. This purchase is determined by whether the molecule can be primary, supplementary, or tertiary. 2-bromo-2-methlypropane & AgNO3 & (CH3)2CO AgBr + ethyl-t-butylether + isobutylene

Figure 2: The SN2 system of 2-bromo-2-methlypropane with AgNO3 in (CH3)2CO. The SN2 reaction mechanism is a one-step, bimolecular shift in which the bond-breaking and bond-making processes arise simultaneously. The SN2 response requires a strong nucleophile. The order of reactivity is a opposite from the SN1 reaction because the nucleophile must assault from the back, and is preferred with the least steric burden. The halide attached to a primary carbon is a lot easier to attack from the backside. In experiment one, the 1-chlorobutane was the most preferred reactant and then the primary 1-bromobutane, the extra 2-bromobutane, plus the tertiary 2-bromo-2-methylpropane. This purchase is determined by whether or not the molecule is primary, second, or tertiary. " SN2 reactions are extremely sensitive to steric factors, since they are greatly retarded simply by steric burden (crowding) at the site of reaction. Generally, the order of reactivity of alkyl halides in SN2 reactions is: methyl > 1° > 2°. The 3° alkyl halides are so packed that they tend not to generally respond by an SN2 mechanism. ”1 1-chlorobutane and NaI-acetone ------> 1-iodobutane + NaCl (precipitate) Generally speaking, weaker angles make better leaving groups. SN1 and SN2 reactions show the same developments, but SN1 is more sensitive. The reactants favored inside the SN2 mechanism are the opposing of the SN1 reaction. the principal 1-chlorobutane was most favored, followed by the principal 1-bromobutane, the secondary 2-bromobutane, and tertiary 2-bromo-2-methylpropane. Desk 1: Stand of Reagents with molecular weight, denseness, melting stage, and cooking point. Name| Molecular Excess weight (g/mol)| Denseness (M/V)| Shedding point (°C)| Boiling level (°C)| 2-bromo-2-methylpropane|...