Tutor profile: Domonkos P.
Subject: Organic Chemistry
Describe the differences and similarities between soft and hard nucleophiles in Organic Chemistry. Make sure to discuss the following: size, charge, basicity, energy level of HOMO, functional groups they like to attack and mention some examples for each.
Hard nucleophiles are typically smaller in size with more compact external orbitals whereas soft nucleophiles are larger with more diffuse external orbitals that are easier to polarize. Hard nucleophiles are typically charged whereas soft nucleophiles are typically neutral. More charge means more "hardness" usually. Hard nucleophiles are usually more basic (HX is weak acid) and soft nucleophiles are less basic or not basic (HY is strong acid). Hard nucleophiles have low-energy HOMO and soft nucleophiles have high energy HOMO. As a result, the former is more likely to have a good overlap with low-energy LUMO and the later is more likely to overlap with high-energy LUMO. Hard nucleophiles like to attack C=O whereas soft nucleophiles like to attack saturated carbon. Examples for hard nucleophiles are: RO-, NH2-, MeLi Examples for soft nucleophlies are: RS-, I-, R3P
Describe the characteristics of group 1. and group 2. elements in about 5-10 sentences. Compare and contrast physical and chemical characteristics and show how these change as you go down within a group.
Group 1. elements are alkaline metals and group 2. elements are alkaline earth metals. Members of both groups all appear as solids at room temperature but they have low density and low melting points, which are even more true for group 1. elements. Melting points decrease as we go down within a group. Members of both groups are known for being very reactive, especially towards oxidising agents. Group 1. elements are more rective than group 2. elements and reactivity increases as we go down within a group. Reactions of both group 1. and group 2. elements with water provides metal hydroxides and hydrogen gas, the former gives strong alkaline pH to aqueous solutions. No members of either group can be found in elemental form on earth, thus these elements have to be made by electrolysis.
Subject: Basic Chemistry
Describe what two particles are (or can be) contained in the nuclei of atoms. Briefly describe their roles/characteristics.
Protons are and neutrons can be contained in a nucleus. Each proton gives one positive charge to the nucleus (atom) and the neutral neutrons serve as intermediate bridges between them, thus preventing repulsive interaction between protons.
needs and Domonkos will reply soon.