In order to make sense of this trend, we will once again consider the stability of the conjugate bases. Using the pKa table, determine a suitable reagent (except H3O+ and other inorganic acids) to protonate the following species. Which of the following compounds is most acidic? How to choose a base to deprotonate a given compound - Chemistry Steps The lone pair on an amine nitrogen, by contrast, is not part of a delocalized p system, and is very ready to form a bond with any acidic proton that might be nearby. We will use a hypothetical acid (A-H) to achieve this: One of the products on the right side is the protonated form (conjugate acid) of the alkoxide which is an alcohol. The formal charge rule applies even more strongly to NH acids. Conversely, acidity in the haloacids increases as we move down the column. The most acidic group is the protonated amine, pKa ~ 5-9, b. Alpha proton by the C=O group, pKa ~ 18-20. 100% (18 ratings) Transcribed image text: Which is the most acidic proton in the following compound? Next, we can react this with a hypothetical base, abbreviated as B. The first model pair we will consider is ethanol and acetic acid, but the conclusions we reach will be equally valid for all alcohol and carboxylic acid groups. For example, if you know that ROH, RCO2H, and RSO3H are common acidic functional groups, you'll have no trouble finding acidic groups in the following molecule (the correct groups are marked in red). Essentially it's a case of aromaticity vs number of resonance If we know which sites bind protons more tightly, we can predict in which direction a proton will be transferred. Which of the following has most acidic proton? In general, resonance effects are more powerful than inductive effects. You can explain the acidity of vitamin C by regarding it as a vinylogous carboxylic acid. Most acidic proton in the structure of Ascorbic Acid (Vitamin - YouTube Distillation is a unit operation that separates component substances from a liquid mixture which is shown by the teacher. Simply put, you must scan the molecule for acidic functional groups, and then rank the reactivity of these groups. Because fluoride is the least stable (most basic) of the halide conjugate bases, HF is the least acidic of the haloacids, only slightly stronger than acetic acid. Stack Exchange network consists of 181 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
