Expressions for Ochem answer types
Expressions are evaluators that compare a student’s answer to a correct or wrong answer and give relevant feedback. These evaluators apply to the Ochem answer types (solutionOchemMechanism and solutionOchemSkeletal) which require students to answer by using the MarvinSketch chemical drawing tool.
OChem expressions reference tableExpressions are listed in alphabetical order. Click an expression name for more information. An X indicates whether the expression can be used with the skeletal answer type (solutionOchemSkeletal) and/or the mechanism answer type (solutionOchemMechanism).
| Expression name in authoring | Skel | Mech | Common name and example |
|---|---|---|---|
|
expressionBoolean (for skeletal) or |
X | X | Boolean – This is a special expression container which combines one or more other expressions |
| expressionOchemEvalAtoms | X | X | Atoms – If the total number of C atoms is more than 3 |
| expressionOchemEvalCharge | X | Charge – If the total charge of the response is exactly 1 | |
| expressionOchemEvalConformBond | X |
Bond confirmations - If the single-bond conformation is staggered, eclipsed, gauche, or anti (Available only when the Three dimensional initialization parameter is selected.) |
|
| expressionOchemEvalConformChair | X |
Chair conformation - If the group is axial or equatorial (Available only when the Three dimensional initialization parameter is selected.) |
|
| expressionOchemEvalContains | X | X | Contains – If no compound in the response contains the skeleton with charge, radical, isotope states matching exactly [MRV file] |
| expressionOchemEvalFormula | X | X | Formula – If the response has the molecular formula H2O |
| expressionOchemEvalFunctionalGroup | X | X | Functional Group – If the number of times the functional group chosen below appears in the response is exactly 1 |
| expressionOchemEvalIs | X | X | Is – If no compound in the response is [MRV file] |
| expressionOchemEvalMapProperty | X | Map Property – If the mapping numbers of the response are exactly [MRV file] which contains mapping numbers | |
| expressionOchemEvalMechCounter | X | Number of boxes, reaction arrows, or resonance arrows - If the total number of boxes is less than 4 | |
| expressionOchemEvalMechFlowsValid | X | Electron flow arrows used correctly – If the electron flow arrows in any step do not produce the products expected, except for the following starting materials | |
| expressionOchemEvalMechProdStartIs | X | Starting materials or products present - If the expected starting materials or products are present in the response | |
| expressionOchemEvalMechRule | X | Mechanism rules used correctly - If the student response obeys expected mechanism rules (i.e. and E2 reaction must contain a strong base) | |
| expressionOchemEvalMechSubstructure | X | Expected substructures present – If expected intermediates or transition states and curved arrows producing those species are present | |
| expressionOchemEvalNumMols | X | X | Number of Molecules – If the total number of compounds in the response is exactly 2 |
| expressionOchemEvalRings | X | Rings – If the response has a number of rings that is exactly 2 | |
| expressionOchemEvalWeight | X | Weight – If the exact molecular weight is exactly 2 +/- 0.01 | |
| expressionOchemMechTopology | X | Expected topology – If a linear or cyclic topology is present |
- When a student's response matches an expression, the relevant feedback is displayed.
- Each expression can identify a student’s response as correct or wrong.
- Expressions are evaluated in order starting at the top with Expression 1. Once a student’s response matches an expression, no more expressions are evaluated.
- Expressions can be combined with “and” and “or” to create a single Boolean expression, which must match all (and) or any (or) of the sub-expressions. More on the Boolean expression you can use for evaluating responses to skeletal and mechanism questions.
- For the solutionOchemMechanism answer type: Code each condition that would make the answer wrong, starting with Expression 1. After coding all possible wrong answers, add an expressionOchemEvalAtoms and set the number of carbon atoms to greater than 1. In this way, a student will be marked correct if no error is made. This allows for multiple correct answers to be accepted.