Picking just CH 3 NHNa & C 6 H 5 Li alone was marked wrong. I do not know the co
ID: 1024306 • Letter: P
Question
Picking just CH3NHNa & C6H5Li alone was marked wrong. I do not know the correct base combination or if CH3NHNa & C6H5Li should or should not be on the list as no other feedback was provided.
3. value: 10.00 points 2 1 attempts left Check my work Select all that apply Report problem Which of the following bases are strong enough to deprotonate CH CH2CH2CECH (pKa-25), so that equilibrium favors the products? Hint NaOH CF COONa NaCHy(CO)N(CH3)2 NH CH3NHNa O NaCH2(CO)N(CH3» References eBook & Resources WWTB Question Difficulty. MediumExplanation / Answer
Alkynes contain acidic hydrogens. Hydrogen atom or atoms attached to the triply bonded carbon atoms can be easily removed by means of a strong base.
Acidity of a compound depends on the stability of the conjugate base.
In an alkyne, where the carbon is sp hybridized, the lone pair lies in an orbital with 50% s character [the 2s orbital is closer to the positively-charged nucleus than the 2p orbital, increasing stability].
Compare that to alkenes (sp2, 33% s-character) and alkanes (sp3, 25% s character) and we have an explanation as to why alkynes have a pKa of 25, which is a factor of 1017 more acidic than your typical alkene (pKa about 42) and 1025 more acidic than alkanes (pKa 50).
In order to deprotonate the alkyne usually sodium amide (NaNH2) or Na in liquid ammonia the conjugate base of ammonia (pKa 38) can be used.
So among the given options CH3NHNa can be chosen to deprotonate the alkyne.
Even C6H5Li is also strong enough to deprtonate the given alkyne.
NaOH is not strong enough to deprotonate the given alkyne.
NH3 cannot deprotonate the given alkyne. Even alcohols and alkoxides also cannot deprotonate the terminal alkynes.
NaH is also strong enough to deprotonate the given alkyne.
This can be explained based on their Pkb values.
. In general, an acid and base will react only if the reaction products are a weaker acid and a weaker base than the reagent acid and reagent base. Stated otherly...
Other options also cannot deprotonate the alkyne.