Hi. Could you guys walk me through this OCHEM problem.?

which of the following compound is hydrolyzed most slowly in aqueous NaOH?

a.)R-C-O-C-CH3 (Oxygen double bonded to each C)

b.)R-C-NH2 (Oxygen double bonded to C)

c.)R-C-OCH3 (Oxygen double bonded to first C starting from left)

d.)R-C-Cl (Oxygen double bonded to C)

e.)R-C-OCH2 (Oxygen double bonded to first C starting from left) with a benzene ring attached to CH2.

thanks for the help.

1 Answer

  • Lancenigo di Villorba (TV), Italy

    Your answer interests the ACYLIC NUCLEOPHILIC SUBSTITUTIONs.

    I CHOSEN LETTER b.

    FUNDAMENTs

    The ACYLIC DERIVATIVEs arise the Molecular Structure strictly similar to CARBOXYLIC ACIDs.

    When I draw it

    R-C-G

    .....||

    ....O

    I sketched the interested Compounds when I define appropriately G.

    As you know, RC(=O)G is the SUBSTRATE or the Compound undergoing the Nucleophilic Substitutions.

    On the other terms, Substrate acts as an ELECTROPHILIC REACTIVE since the CARBONYLIC carbon inside the molecule results its own ATTACK's SITE.

    These latter place undergoes the Nucleophilic Reactive Actions (e.g. it may be Sodium Hydroxide or NaOH).

    MOLECULAR COMPARISON

    WHICH ARE THE VARIABLEs INFLUENCING THE REACTION's RATE?

    As you know, Temperature and Reactive's Concentrations are the Main Ones : besides them, I will treat on the Factors inside the Molecular Structure in RC(=O)G.

    The Factors are :

    -) Molecule's Planarity ;

    -) Electrophilic Nature of Carbonylic Bond ;

    -) Weakness Nature of G's Bond.

    ALL THE ACYLIC DERIVATIVEs satisfy the former request, e.g. CARBONYLIC Carbon Atom obey to sp2 or Trigonal or PLANAR HYBRIDIZATION.

    Some Acylic Derivatives result able to enhance the Electrophilic Nature of Carbonylic Bond, e.g. the ACYLIC DERIVATIVEs ARISING "G" AS ELECTRON-ATTRACTOR GROUPs.

    Some Acylic Derivatives result unable to displace its own Electron Pairs or Duets above the Carbonylic Carbon Atom so they cannot strenghten the Chemical Bond involving G Group, e.g. the ACYLIC DERIVATIVEs ARISING "G" AS OXYGEN, NITROGEN or HALOGEN-BASED ONEs.

    The resulting Scale's Order is

    MOST FAST > d.) > a.) > c.) > e.) > b.) > LEAST FAST

    CONCLUSION

    You are seeking for the ACYLIC DERIVATIVE UNABLE TO UNDERGO FAST NUCLEOPHILIC SUBSTITUTION.

    By applying the overwritten criteria, I choosen AMIDEs or NITROGEN-BASED ACYLIC ONEs.

    I hope this could be clear.

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