CHM419: COMPLETE BREAKDOWN ON PHYSICAL ORGANIC CHEMISTRY

By | September 30, 2019

CHM 419 PHYSICAL ORGANIC CHEMISTRY (COURSE OUTLINE)
  • Preparation and reactions of stereoisomers.
  • Stereo selectivity, neighbouring group effects and a few special topics in physical organic chemistry.

MATERIAL ONE : WHAT YOU SHOULD KNOW

PART A

COMPLETE BREAKDOWN ON PHYSICAL ORGANIC CHEMISTRY

.Using appropriate examples explain the following stereochemical terms: enantiotopic hydrogen, erythro enantiomer, optical purity, stereoselectivity, diastereomer ,pro-chirality, racemic mixture, diastereotopic hydrogen
.a compound has a specific rotation of -39.0°, a solution of the compound (0.187 g/mL) has an observed rotation of -6.52° when placed in a polarimeter tube 10cm long. What is the percent of each enantiomer in the solution
. Each of the following reaction was carried out, and the product were separated by careful fractional distillation or recrystallization : monochlorination of (R) -sec-butyl chloride at 300°c, monochlorination of racemic sec-butyl chloride at 300°c. For each reaction indicate how many fractions will be collected. Draw stereochemical formula of the compound or compounds making up each fraction and give each R/S specifications. Indicate whether each fraction as collected will show optical activity or inactivity
.using equation of reaction only, illustrate the three main types of PERICYCLIC reaction
.using the concept of molecular orbital theory to determine the stereochemistry of reaction product by:
– how many π molecular orbital present in 1,5,8-decatrine are responsible for bonding.
– indicating (by adopting psi notation, Φ) the HUMO , LUMO, HOMO and LOMO at the ground state
-indicating all the antibonding molecular orbitals
– how many nodes are present in Φ2*
– what is/ are the symmetric molecular orbitals
.illustrate how the electrocyclic ring closure of ( 2E,4Z,6E)-2,4,6- octariene can yield a stereospecific single product with cis methyl groups on the ring.
.What are reactive intermediate
.illustrate with equations one method of preparation and two reactions of aryne
.write complete equations of the following reaction : methylene cyclohexene and methyl propenoate, propene and ethylene in presence of heat , 1,3,5 – hexatrine and heat, 2,4,6-octatriene and heat, photolysis of ketene
.using the concept of molecular orbital theory of stereochemistry of reaction products: draw the π molecular orbital of 1,3 -butadiene. Indicate in tabular form by adopting psi notation the frontier orbital HOMO and LUMO before and after photolytic excitation
.what is the number of nodes in psi2 and psi4
.what are the symmetric molecular orbital

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.what stereospecific cyclic product is formed if (2E,4E)-2,4-hexadiene undergoes photochemical electrocyclic reaction
.the synthesis is dimethyl bicycling (2.2.1)bepty-2-ene -trans-5,6-dicarboxylate was accomplished through the Dies-alder reaction of 1,3-dichloro-1,3-cyclopentadiene with dimethyl fumarate (CH3OCOCHCHCOOCH3) . Show the reaction mechanism and the structure of the bicyclic product.
.given that the molar enthalpy of combustion of solid cyclohexanone, carbon and hydrogen are -841.1 ,-94.0 and -68.3kcal/mol. Calculate the molar enthalpy of formation of cyclohexanone
.the group contribution of C-H, C-C, and -C=O bonds to the molar enthalpy of formation Of cyclohexanone are -3.83,+ 2.73 and -14.4 kcal/mol . Use the data to estimate the molar enthalpy of formation of cyclohexanone and compare your result with the obtained value above
.the bond length and overall charges of 1,2 dichlorobenzene 1,3- dichlorobenzene and 1,4- dichlorobenzene are 4.79, 3.23,and 2.45A and 0.1 ,0.1 and 0e respectively : calculate the quantity of dipole moment of each molecule. Comment on the variation in the polarity of the molecules [1Debyne=1×10-18esu . Chm, 1e=4.8×10-10esu ]
.given the molar enthalpy of combustion of carbon (graphite) . Hydrogen and acetone [(CH3)2 CO] are -94.0,-68.3, -427.8 kcal/mol respectively. estimate the molar enthalpy of formation of acetone.
.the group contribution of C-H, C-C and -COC bonds to the molar enthalpy of formation of acetone are -3.83,+2.73 and 14.4kJmol-¹ respectively. Use the data to estimate the enthalpy of formation of acetone and compare your result with the value obtained above
. The enthalpy of hydration and dehydration of cis -2-butene and trans-2-butene are -19.2 and +17.9kJmol-¹ respectively. Estimate the relative difference in heat of formation of the 2 isomers , suggest reasons for the higher stability of more stable isomer
.what are relative intermediate. illustrate with equations, one method of preparation, and two reactions of aryne,
. write complete equations for the following reactions: methylene cyclohexene and methyl propenoate
.the conversion of but-1-ene to 2-bromobutane is non stereoselective . Use suitable chemical equation to illustrate this observation and state the configuration of the product formed
.what is the composition of enantiomeric mixture wit 20% ee
.using appropriate examples explain the following stereochemical terms : erythro enantiomer , enantiotopic hydrogen, diastereomer, pro-chirality, racemic mixture, stereoselectivity, optical purity, diastereotopic hydrogen

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PART B

 

  • Learn how to Classify a reaction as an electrocyclic reaction or a cycloaddition. Label the sigma bonds that are
    broken or formed in each reaction.
  • draw the molecular orbitals for 2,4-hexadiene, Label the HOMO and the LUMO in the ground state, Label the HOMO and the LUMO in the excited state
  • How many pi molecular orbitals are present in 1,3,5,7,9-decapentaene

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