Peter Parker is looking for new materials for his synthetic web. Materials generally involve polymers, which are long, repeating molecules, which can be linear or branched, which can have molecular masses in the order of thousands or tens of thousands of Daltons. To prepare polymers, advanced reactions are usually required, such as coupling reactions, Ziegler – Natta, advanced oxidations, among others. The characteristics of the polymer depend of the properties of the geometry and polarity of its precursors, so Parker decides to study different precursors proposed by Tony Stark. Help Parker with his investigation: a) Stark proposes to Parker that he can use some anions as crosslinking ligands between cationic polymers to increase the strength of your webs. He proposes you to try the anions of sodium dithionite (Na2S2O4), lithium borohydride (LiBH4), calcium hexafluorophosphate (Ca (PF6)2), ammonium fluorophosphate ((NH4)2PO3F) and sodium thiosulfate (Na2S2O3). Propose the most probable Lewis structure of each anion. Determine its molecular geometry, angles of bonding, formal charges, and hybridization around each central atom.

Chemistry: Principles and Reactions
8th Edition
ISBN:9781305079373
Author:William L. Masterton, Cecile N. Hurley
Publisher:William L. Masterton, Cecile N. Hurley
Chapter23: Organic Polymers, Natural And Synthetic
Section: Chapter Questions
Problem 51QAP
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Peter Parker is looking for new materials for his synthetic web. Materials generally involve polymers, which are long, repeating molecules, which can be linear or branched, which can have molecular masses in the order of thousands or tens of thousands of Daltons. To prepare polymers, advanced reactions are usually required, such as coupling reactions, Ziegler – Natta, advanced oxidations, among others. The characteristics of the polymer depend of the properties of the geometry and polarity of its precursors, so Parker decides to study different precursors proposed by Tony Stark.

Help Parker with his investigation:

a) Stark proposes to Parker that he can use some anions as crosslinking ligands between cationic polymers to increase the strength of your webs. He proposes you to try the anions of sodium dithionite (Na2S2O4), lithium borohydride (LiBH4), calcium hexafluorophosphate (Ca (PF6)2), ammonium fluorophosphate ((NH4)2PO3F) and sodium thiosulfate (Na2S2O3). Propose the most probable Lewis structure of each anion. Determine its molecular geometry, angles of bonding, formal charges, and hybridization around each central atom.

 

b) Peter reads in a book on Organic Chemistry that “if a molecule has resonance, it will be more stable". Will any of the ions have resonant structures? Identify those who have resonance and draw all its resonant structures. Peter also reads that the more resonant structures have a molecule, the more stable it will be. According to your criterion, Which anion will be the most stable?

 

c) Another strategy that Tony recommends to Peter is to use oxime-based polymers, which allow the cobweb not only to improve its resistance, but also to absorb substances such as metal ions that allow it to conduct electricity. Parker finds in a book on Organic Synthesis that he can prepare oximes using the reaction of hydroxylamine (NH2OH) and formaldehyde (CH2O) to generate formaldoxime (H2CNOH), according to the following reaction:

NH2OH(g) + CH2O(g) −−→ H2CNOH(g) + H2O(g)

Propose valid Lewis structures for all the reactants and products of the formaldoxime synthesis.

 

d) Determine the molecular geometry and polarity of hydroxylamine, formaldehyde, and formaldoxime. Justify your deductions. Is there a difference between reactants and products for both features?.

e) According to the Lewis structures, estimate the reaction enthalpy for the synthesis of the formaldoxime from bond enthalpies.

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