Question

6. (4 points) Which of the following statements best explains the pka difference between cyclohexanol and phenol? a. cyclohexanol has a lower pka than phenol because spoxygens anions are more stable than sp? oxygen anions. b. phenol has a higher pka than cyclohexanol because the conjugate base is resonance stabilized C. cyclohexanol has a lower pKa than phenol because pi-bonds destabilize the conjugate base of phenol d. phenol has a lower pKa than cyclohexanol sp'oxygens anions are more stable than spoxygen anions. 7. (4 points) How are the following compounds related? CHE CH H CHE *CH a. enantiomers b. diastereomers c.identical d. constitutional isomers 8. (4 points) Which reagents are needed to convert 1-octyne to 2-octanone? a. ozone followed by dimethyl sulfide b. hydrogen gas with a transition metal catalyst C. BHz in THF followed by NaOH, peroxide, and water d. HgSO4, H2SO4, and water 9. (4 points) How many stereoisomers are possible for 1-bromo-6-methyl-4-heptene-2-ol?

6) Which of the following statements best explains the pKa difference between cyclohexanol and phenol?

7) How are the compounds related?

8) Which regeants are used to convert 1-octyne to 2-octanone

9) How many stereoisomers are possible for bromo-6-methyl-4-heptene-2-ol?

Answer 1

solution :

cyclohexanol and phenol both belongs to the category of alcohol.

As alcohol can loose H+ ion so they are arhenius acid.

acidity is directly proportional to ka value. that means if an acid is strong it will more dissociates and will produce more H+ ion.

so a strong acid will have ka value large.

pKa = - log ka

that is if Ka value is high pKa value will be less .

conclusion : strong acid will have less pKa value.

in cyclohexanol all carbon are sp3 hybridised whereas in phenol a complete chain of delocalised pi electron is available which is resonance stabilised. so conjugate base of phenol is more stable. hence phenol is more strong acid than cyclohexanol hence value of pKa is less.

cyclohexanol (Not resonance Stabilisea) ا س ۵ H phenol وع جع Resonance stabilised وم وه

phenol has a lower pKa than cyclohexanol and sp2 oxygen anion are more stable than sp3 oxygen anion.

hence option d is correct answer

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