Question

2. Place the following in order from greatest to least Brønsted basicity (i.c. highest to lowest pKa of conjugate acid). a. PPhs, PMes, NMe b. PhMeN, Ph2N', MerN, 'Pr2N

Answer 1

Answer (2) Phạp, ponez, Nmez The order from greatest to least Bronsted basicity is Nme > Pmez > Php Phụp has a propeler shaped structure which is highly stable . The lone parr of p atom is in resonance with the 3 ph group. So tome it can't accept the proton and the conjugate acid is highly unstable In pMez the 3 me group with tI effect increases the election density of p atom But p atom is less electronegative and large in size. So it can de localized the electron density into its orbitals. So it can't abstrat proton easily, and the tre can charge on patom meat makes the conjugale aid less stable. pme + Hmez. In case of aromes the 3 me group with I effect increases the electron density of N atom . Because of wish electronegativity and smallersize it can easily abstract

a proton and the conjugate and is sto Nmez tHt - Abones pka value is low ③ Phment, Phan, Mesa, "PEN The order is iPr N > Men > Phmen > Phan In Phan the ove charge on N atom can delocalised in 2 ph ring make electron defficient. The conjugate suid is less stable. Abstrate pooton is not so easily. In Phned the me group has 4 I effect and Ph group has -R effect, Natom is electron defficient but not in much It can not easily abstrat the proton. Conjugte acid is less stable. In men, the 2 me group has t I effect makes N atom ting electron rich. Proton abstraction is easy and conjugate acid is stable. In iPr, N, the zipp group has more I effect than me group make Natoon highly electron rich. Proton abstraction is more easy and conjugate acid is more stable,