Question

2. (4 pts) Poly(vinyl alcohol) (PVA) is a commercially available polymer that can be synthesized by chain-growth polymerizations. However, using the vinyl alcohol monomer does not work. » AIBN , tit Он 65°С No polymerization! a) Briefly explain why vinyl alcohol doesn't work for this polymerization. What compound would form in the scheme shown above? b) Propose an alternate route to the synthesis of PVA.

Answer 1

Vinyl alcohol is a very unstable compound. It can easily get converted into acetaldehyde, a stable resonance Structure of vinyl alcohol Thus, vinyl alcohol and acetaldehyde are called tautomers interconvert able structural isomea This proues of interconversion is called tautomerization OH Vinyl alcohol aulude de Mechanism -- autaldehyste Vinyl alcohol . Hence at a particular time, Vinyl alcohol getting converted to autaldehyde. This is the season why vinyl alcohol do not undergo Polymerisation easily to form Polyvinyl alcohol

• Hence, to prepare the desired polymer (PVA), we have to Stop this tautomerization • A strategy used for stopping tautomerization is protection of OH group By treating vinyl alcohol with autic acid, we can convert it to Vinylactate, which do not undergo tautomerization Hence the alcohol group is protected from converting to aldehyde using the protecting group - acid t .. Vinyl alcohol a ch'eau'd Vinyl autala • Vinyl aulate can be easily polymerized by AIRN to form Polyvinyl acetate folyvinyl autute (PA)

PVN can be converted to PVA by base hydroly's (An alcohol like ethano) can be used). PVAC PVA This is the alternative method for producing PVA

Nr. AIBN - 8.2. azobis - isobutyrylnitrile HC-C-N=N-C-CH₂ It is a radical initiator This compound have the ability to break itself into radicals - + NEN + .C- c - C-N=N, Ć-CH. HTUU VU" 3 CN These formed radicals can attack the double bond in vinyl mokemer and can further initiate polymeaization CH3 1 =s - WC- + CROA 3 Soon "C- & -c-c-c-c. 3 ) polymer. )

In the first part of the question, OH the two possible radicals Since because of tautomerization, formed will be O1 06 Possible products 0 0