Please explain the reactions with 15% Nal in acetone 40 Lab Partner Ccl crolyl c
ID: 588543 • Letter: P
Question
Please explain the reactions with 15% Nal in acetone40 Lab Partner Ccl crolyl chlonde 3 st - i min - Non rtac - bro lohuxone sec (clo Shake tach tot wbe tcord hme neaded to fom prtipihale ck betwtun:dunse prtpale, cleudi ess altr 5 mins plau an ith ho upitaksino hot wor bath at aftr mm coo noht wutkur a rachen has occurnd Observohons Hak withn 3mins 2-Chlersbutane Los mechint betause Cloud cloud 1- Bromebutore Crotyl Chlerid nzyl Chlen rome benzn i5se clourl min min clev Date Date Note: Insert Divider Under Copy Sheet Befone Writ THE HAYDFN-McNEIL STUDENT LAB NOTEBOOK
Explanation / Answer
Here there are two separate processes which are being used to determine alkyl halides. In the observations that has been made it is not mentioned weather first method is used which is NaI test or second one which is Silver halide test. Both are two different mechanism which complement each other. Let us discuss them briefly which will be able to explain the results obtain in the table.
1- Silver halide test : The following reaction takes place: RX + AgNO 3 ------> AgX + RONO2
This is Unimolecular nucleophilic substitution: where RX first dissociates into cation and halide anion leaves the reactant and acts as a leaving group. We know that reactivity for SN1 reaction is Primary < secondary < tertiary. Benzylic and allylic groups also reacts fast because of resonance stabilisation of carbocation while aryl groups are not reactive towards SN1 reactions.
This can explain the observations made into the table : Bromobenzene is unreactive, while crotyl chloride ( allylic system ) and benzyl chloride gives positive response. Also leaving group matters for SN1 reactions, Bromide is a better leaving group than chloride so it will react faster. 2-chlorobutane will take more time and require more efforts for reaction than 2-bromobutane. Simmiliar case is there for 1-chloro and 1-Bromo butanes.
2: Sodium Iodide test: This test is based on SN2 mechanism and reaction takes plase as follows :
RX + NaI -------> R-I + NaX In this reaction trend is reversed than the previous case : primary > secondary > tertiary
WIth the help of these two test and by understanding of the mechanism one can reach to the conclusions for the observations and also for the structures of alkyl halides.