Tutor profile: Norberto O.
Subject: Organic Chemistry
The first step in the production of a particular quinazoline requires the reaction of 2-Amino-5-bromobenzonitrile with phenyl magnesiumbromide. This reaction is carried out using ANHYDROUS THF as a solvent and the reaction mixture is refluxed under nitrogen atmosphere for 3 hours. 1. What kind of reaction is this? 2. Why is anhydrous THF specifically used and not just THF 3. Why is the reaction performed under nitrogen atmosphere (or sometimes Argon)
1. This is a grignard reaction. 2. The grignard reagent is highly sensitive to water and will react readily with it. A bottle of THF may well contain residual moisture in it. This is why anhydrous THF (obtained by distillation or from a pure-solvent system) is used. 3. Again this has to do with the grignard reagent's reactivity with moisture. Moisture in the air from humidity is more than enough to disrupt the reaction from occuring properly. This it is carried out under an alternate gas atmosphere - typically as gas that is more dense than air. An air sensitive synthesis.
Jane tried to neutralize 20 mL of a Sodium Hydroxide solution by adding 1 molar equivalent of conc. HCl to the solution. To her surprise the solution was not neutral but rather highly acidic. Explain to Jane why her attempt at neutralizing the basic solution failed. Specifically refer to pH.
The pH of a solution is calculated as negative log of hydronium ion concentration. The key word here is log. Both pH and pOH are logarithmic functions meaning that they do not increase/decrease at a constant (linear) rate. This is why neutralizing a solution is not as simple as adding an equivalent amount of acid/base. Instead attention to the desired pH and its respective hydronium concentration must be considered.
Subject: Basic Chemistry
What is the molecular geometry of a water molecule? Give a reasonable explanation as to why it has the geometry it does. Hint: Think about the electronic geometry.
A water molecule is bonded to two hydrogen atoms. However - the octet rule tells us there must be 8 electrons on the oxygen atom. Therefore there must also be 2 lone pairs. The electrons maximize there distances from each other and thus take on a tetrahedral electronic geometry. But because the oxygen only has two bonds its appearance is a "bent" molecular geometry.
needs and Norberto will reply soon.