Computational Chemistry Lab: Part 2

Introduction

In this lab we are going to extend the work from your 1st lab to study some slightly more complicated molecules. You will be extending the wiki you started in the first lab.

The Hunt research group studies new materials called ionic liquids (ILs), these are liquids completely composed of ions, but unlike molten salts which melt at high temperatures (above 800 °C), ILs have room temperature (and below) melting points. Ionic liquids are new solvents with extremely useful properties and are of intense current interest. For example, ILs do not evapourate and so no explosive volatile vapour is produced making them safer to use, and greener. ILs make great electrolytes, due to a high solvating ability. The low melting point means much less energy is needed when compared to molten salts.

ILs are formed from larger less symmetric ions than simple salts, one example is the imidazolium cation ILs. The smallest imidazolium has methyl groups, but more ILs can be made by adding longer alkyl tails, or functionalising the substituents. ILs are highly chemically tunable.

IL cations also tend to have H-bond donor sites, and the anions H-bond acceptor sites. ILs undertake novel forms of hydrogen-bonding, particularly the new "doubly ionic H-bond" which only exists because of the stabilisation of the ionic environment.

In this lab you are going to explore some aspects of ILs and the doubly ionic H-bond.

Computational chemistry is resource intensive and we would normally (in a research setting) use an HPC (high performance computer). To keep the calculations on the IL at a level the computers here can handle we are going to use a poor "basis set" called 3-21G (you will learn what this means in the comp chem course!). You should be aware that we would normally use a 6-31G(d,p) basis as the minimal basis.

REALLY important Reminder! We expect you to ASK FOR HELP, don't just keep repeating calculations. If you cannot see, or don't understand why your job has failed there is no point in repeating it.

REALLY important

  • During this part of the lab you will receive feedback as part of the process, this will be via the demonstrators when they answer your questions.
  • Demonstrators are available 1-4pm on Wednesday and Friday. You are able to continue to work until 5pm, but there will be no demonstrator present. You can also work on the wiki at home. Support is only provided in the lab by the demonstrator.
  • You will be assessed via a wiki and through submitted job files. The lab will be graded out of 30
  • You must complete the lab in the period assigned, we will check the start and end time-stamp of your wiki. The bonus is you don't have to "hand" anything in on the due day. Your lab is due on the Friday the week after your lab week
  • Marking You will receive brief comments directly to your wiki and a grade uploaded to Canvas (Nuku)
  • If you are ill and/or have a personal problem contact Prof. Hunt BEFORE the lab is due, Prof Hunt *may* offer a 24hr extension. Items of work submitted after the due date will incur a penalty mark (detailed in your Lab Manual) unless there are special circumstances. If you are running into any personal or time management problems, it is always best to contact Prof. Hunt.

General points

  • timing/workload you should be able to complete ALL the calculations and start adding to your wiki in the 8 hours of the lab. You are expected to put at least another 2 hours work outside of lab hours to obtain a pass grade and a few more hours to obtain a high grade. If you find yourself falling behind do contact Prof Hunt or one of the demonstrators, we are there to help!

  • time management! this lab is easy to do out of lab hours, which allows you some flexibility, BUT this does not mean you should spend large amounts of time on it! In computational chemistry problems can be hard to work around on your own, take advantage of the demonstrators experience. Manage your time wisely. Help with the lab is only available within lab hours.

  • enjoying the lab the point of the lab is to learn new skills, be exposed to computational chemistry and have fun! We want you to enjoy the lab, if you find yourself getting frustrated, repeating calculations, running in circles, contact us, we can help!

  • collaboration research is normally undertaken in a research group; people help each other, compare and discuss results. We do encourage collaboration! If you compare your results with another researchers work you should acknowledge them by name and include a link to their wiki, if you choose to do this you should also discuss the relevance of any similarity or difference in your results. It is not appropriate for you to copy the work or material from another person. important Copying or using another persons work or files will be treated as plagiarism and carries very serious consequences

use the links in the pannel to the left to navigate through the lab

Rough marking guide (out of 30)

  • wiki formatting, graphical representations 5 marks
  • NH3 and BH3 dissociation energy 5 marks
  • Me3NH-Cl scan 5 marks
  • ionic-liquid ion-pairs 15 marks
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