Question

What is the reaction order with respect to initiator concentration (e.g. first order, second order, etc.) for each of the following steps:

a. Initiation

b. Propagation

c. What is the relationship between initiator concentration and critical chain length?

Answer 1

A. INITITATION:A REACTION OR PROCESS GENERATING FREE RADICAL(OR SOME OTHER REACTIVE REACTION INTERMEDIATES)  WHICH THEN INCLUDE A CHAIN REACTION.FOR EXAMPLE, IN THE CHLORINARINATION OF ALKANES BY A REDICL MECHANISM THE INITIATION STEP IS THE DISSOCIATION OF MOLECULAR CHLORINE.

B. PROPAGATION:CHAIN PROPAGATION IS A PROCESS IN WHICH A REACTIVE INTERMEDIATE IS CONTINUOUSLY REGENERATED DURING THE COURSE OF A CHEMICAL CHAIN REACTION.FOR EXAMPLE , IN THE CHLORINATION OF METHANE , THERE IS A TWO - STEP PROPAGATION CYCLE INVOLVING AS CHAIN CARRIERS A CHLORINE ATOM INVLOVING AS CHAIN CARRIERS A CHLORINE ATOM AND METHYL RADICAL.WHICH ARE REGENERATED ALTERNATELY:

CL+ CH4  HCL+CH3

  CH3  + CL2 CH3CL+CL

THE TWO STEPS ADD TO GIVE THE EQUATION FOR THE OVERALL CHAIN REACTION :

CH4 + CL2    CH3CL+HCL

C. THE RELATIONSHIP BETWEEN INITATOR CONCENTRATION AND CRITICAL CHAIN LENGTH :

THE CRITICAL CHAIN LENGTH IN ISPERTION POLYMERIZATION IS SYSTEMATICALLY INVESTIGATED UTILIZATING LOW MOLECULAR WEIGHT POLY(METHYL METHACRYLATE) OLIGOMERS SYNTHESIZED BY CATALYTIC CHAIN TRANSFER POLYMERIZATION.THE SOLUBILITY OF THESE OLIGOMERS IN METHANOL/ WATER MEDIA OF DIFFERENT COMPOSITIONS AND AT DIFFERENT TEMP HAS BEEN VISUALLY DETERMINED.THE RESULT SHOW THAT THE SOLUBILITY OF THE OLIGOMERS INCREASES WITH INCREASING METHANOL FRACTION AND INCREASING TEMP. INITATOR CONCENTRATOR KEPT LOW,ATTEMPT TO INCREASE THE RATE OF POLYMERIZATION BY INCREASING THE INITIATOR POLYMERZATION BY INCREASING THE INITIATOR CONCENTRATOR RESULT IN THE PRODUCTION OF POLYMER WITH A LOWER AVG MOLAR MASS.