A student writes the following explanation of how one type of compound is formed.
1 answer:
Answer:
<u>Polymerization process(Addition)</u>
Explanation:
<u>Polymerization </u>: The process in which small units called monomers combine to produce large mass compound is called polymerization reaction.These large masses are also called macromolecules.
The formation of polymers can occur by addition or condensation process .
<u><em>Addition</em></u> : In addition reaction small units add to previous units
<em><u>Condensation</u></em> : In condensation , a small molecule like water , carbon dioxide get eliminated when the unit attach to previous unit.
Some natural polymers are Proteins , carbohydrates , lipids , cellulose.
Polythene = addition polymerisation also known as Chain growth polymerisation.
This occur in three steps:
1. Chain Initiation : The start of the reaction occurs with the radical. These are generated from some organic peroxide and have general representation:
2 . Chain Growth = When the small units goes on adding to the previous units , Chain length increases and this is called chain growth.
3. Chain Termination = The chain continues to grow more and more until not forced to stop. This termination of chain growth is called chain termination
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Answer : The correct answer for a) 4-bromo-2-iodo-4-methyl pentane and b)5-bromo-2-ethoxy-2-methyl pentane.
A) Reaction with NaI :
Reaction of alkyl halide with NaI is known as Finkelstein Reaction . The acetone is used as solvent . It involves bimolecular nucleophillic substitution rmechanism (SN²) . There is replecement of one halogen with other occurs .
The incoming Nucleophile(Nu⁻) (halide) attacks on carbon from back side , while the leaving group (halide) leaves the compound from front side , simultaneously. The product so formed have is inverted .(Image)
NaI releases I⁻ ion which act as nucelophile and attacks on C1 carbon and Br⁻ from C1 carbon is released . Out of two bromines at C1 and C4 carbons , C1 is primary carbon which is less sterically hindered while C-4 is tertiary carbon and sterically hindered . So it is easy for incoming Nu⁻ to attack on C1 carbon .So Br⁻ is repleaced by I⁻.
1,4-dibromo-4-methylpentane + NaI → 4-bromo-1-iodo-4-methylpentane
The product formed from reaction between 1,4-dibromo-4-methylpentane and NaI is 4-bromo-1-iodo-4-methylpentane . (Image)
B) Reaction with AgNO3 :
Reaction of alkyl halide with AgNO3 in ethanol takes place via SN¹ ( unimolecular nucleophilic substitution ) mechanism . In this leaving group(halide) leaves from alkyl halide forming an intermediate carbocation species . The incoming Nu⁻ attack on this carbocation.
AgNO3 reacts releases Ag⁺ion which abstract Br⁻ of C-4 carbon from 1,4-dibromo-4-methylpentane. THis forms tertiary carbocation which is more stable than carbocation formed by removal of Br from C-1 . The ethanol being more Nucleophilic than NO₃⁻ (from AgNO₃), attacks on this carbocation .(Image )
The product formed as a result is 5-bromo-2-ethoxy-2-methyl pentane.
