CHM2210 Ch. 2 Alkanes & Cycloalkanes
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danamarie26 on August 2, 2012
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32 terms
Terms | Definitions |
|---|---|
 Comment on the level of saturation of alkanes. | It's saturated. |
| Comment on level of saturation of alkenes and alkynes. | They're unsaturated. |
| What are the 4 types of hydrocarbons focused on in this chapter? | alkanes, alkenes, alkynes and aromatics |
| Define constitutional isomerism. | 2 molecules that have the same formula and different connectivity |
| How can you tell how many exact isomers will form? | Impossible. |
| What's the general trend between # of C and # isomers? | As # C goes up, # isomers goes up exponentially. |
| Name the 12 prefixes for naming alkanes by # of C. | meth, eth, bu, prop, pent, hexa, hepta, octa, nona, deca, undeca, dodeca |
| What is an alkyl group? | alkane with 1 H removed so it can bond to something else |
| Iso- means what in a branch? | It's symmetrical |
| What are the 4 basic steps for naming molecules by IUPAC? | -find main chain -number main chain that gives substituents lowest # possible -name alkyl substituents -list alkyls by alphabetical order, associate C # onto the alkyl, finish with the parent name from the main chain |
| What's the general formula of cycloalkanes? | CnH2n |
| What is the prefix representing cycloalkanes? | cyclo- |
| What are bicyclic molecules? | molecule containing 2 or more rings |
| Differentiate between fused and bridged rings. | fused - rings that share 2 adjacent C and bond between them bridged - rings that share 2 non-adjacent C and bridge between them |
| How do you name bicyclics? | -count total # of C in ring system -[x.x.x.] format -first x is # of C left of bridge -right x is # of C right of bridge -middle x is # C in bridge |
| What are the 2 types of general conformations of an alkane? | staggered and eclipsed |
| Is staggered or eclipsed more stable and why? | staggered; methyl groups are not as close to each other |
| Define Newman projections. | looking at a C-C molecule from the front or back |
| What are the 3 specific forms conformations take? | eclipsed, gauche, anti |
| Which of the 3 specific forms of conformations has the lowest and the highest energy and why? | eclipsed - highest b/c methyl groups too close to each other so molecule is unstable anti - lowest b/c methyl groups are far away as possible so molecule is stable |
| Define torsional energy. | energy associated ith turning methyl group from staggered to eclipsed |
| What's the general trend between torsional energy and # of C? | The more C, the more torsional energy needed to move it |
| Define angular strain. | tendency for molecules to acheive the optimum 109.5 degrees |
| Define steric strain. | strain caused by forcing two methyl groups toward each other (like pushing two magnets together of the same charge) |
| What is the angular strain and torsional energy in cyclohexane? | None |
| What if you can't get the Newman projection to become completely anti? | Deal with it and try to get as close to anti as possible. Methyl gets priority in separation. |
| What's the best conformation for cyclohexane? | the chair conformation that puts the big C substituents as equatorial |
| What happens when we convert one chair to another? | axial goes to equatorial and equatorial goes to axial but the general upward and downward direction in original form is conserved in new form. |
| Why is it better for C substituents to be equatorial? | It allows them to space out better. |
| What does cis and trans mean in stereoisomerism? | cis - same side trans - opposite side |
| What are stereoisomers? | Isomers that differ only in spatial orientation of substituents |
| How do you determine which chair conformation is more stable? | Find the one which has the most substituents as equatorial. |
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