cap. 2 Flashcards
newman projections, conformations, kinetics, equilibrium, stereochemistry (52 cards)
1
Q
formula for alkanes
A
CnH2n+2
2
Q
small alkanes have low bp, so they’re typically
A
gases
3
Q
homologous series
A
a series of compounds that only differ in the number of methylene groups
methylene- CH2
4
Q
carbons in methane
A
1
5
Q
carbons in ethane
A
2
6
Q
carbons in propane
A
3
7
Q
carbons in butane
A
4
8
Q
carbons in pentane
A
5
9
Q
carbons in hexane
A
6
10
Q
carbons in heptane
A
7
11
Q
carbons in octane
A
8
12
Q
carbons in nonane
A
9
13
Q
carbons in decane
A
10
14
Q
iupac rules
A
- find the longest continuous chain of C and use this as the base of the compound
- number the longest chain and start with the end that’s closest to a substituent
- name the groups attached to the longest chain as alkyl groups
- write the alkyl groups in alphabetical order
15
Q
conformation
A
rotation around a C-C single bond
16
Q
steric hindrance
A
when 2 fat molecule groups are near each other
17
Q
physical properties of cyclocalkanes
A
- nonpolar
- relatively unreactive
- bp and mp will depend on molecular weight
18
Q
when does a cycloalkane become a substituent instead of a main form?
A
when the acyclic portion of a molecule contains more carbons than the cyclic part
hexane will become the main component instead of pentane, for example
19
Q
what is the hybridization and bond angle of cyclocalkanes?
A
sp3, 109.5°
20
Q
torisional strain
A
- when all bonds in the cycloalkane are eclipsed
- usually in molecules with eclipsed conformation
21
Q
angle strain in cyclobutane
A
- compresses from 109.5° to 90°
- leads to nonlinear overlap, and bent bonds (sp3)
22
Q
heat of combustion
A
- amount of heat that is released when a cmpd is burned with excess oxygen (in sealed calorimeter)
- if the cmpd has extra energy as a result of ring strain, the extra energy is released in the combustion
23
Q
torisional strain in cyclopropane
A
all C-C bonds are eclipsed, so the entire ring is strained
24
Q
torosional strain of cyclopropane (planar)
A
- angle strain goes from 109.5° to 60°
- torosional strain, eclipsed nature
25
cyclic compounds with 4+ carbons will adopt ___ to relieve ring strain
nonplanar conformation
26
cyclobutane adopts a folded conformation by
eclipsing hydrogens
27
how cyclopentane reduces strain
slightly folds like an envelope so that CH2 groups are eclipsed
28
what is the most stable conformational isomer of cyclohexane?
chair conformation. this one allows the bond angles to actually be 109.5°
29
direction of axial positions
vertical
30
direction of equatorial positions
outward
31
result of axial/equatorial positions during chair-boat-chair conversion?
anything in the axial position becomes equatorial in the next conformation
32
more stable: axial or equatorial?
equatorial. the groups/atoms are pushed outward, so there is less of a chance that bulky groups will be bumping into each other
33
fused rings
share 2 adjacent C atoms and the bond between them
34
bridged rings
share 2 nonadjacent atoms and 1+ C atoms (lit rally builds a bridge)
35
spirocyclic compounds
2 rings share only 1 carbon
36
formula for bicyclic cmpds
bicyclo [#, #, #] alkane
| the #'s are the C on the bridges in descending order
## Footnote
not all C will be in the bridge name
37
mechanism
step-by-step descriptions of how a reaction will happen
38
most reactions need ___ or __ to start
heat or light. for example, the chlorination of methane requires the absorption of 1 photon of light to start a chain reaction
39
initiation
generates a radical intermediate
| formation of radicals from nonradicals
40
propagation
the intermediate reacts with a stable molecule to produce another reactive intermediate
| reaction of radicals to form other radicals
41
termination
side reactions that destroy the reactive intermediate
| rxn of 2 radicals, OR rxn of 1 radical with the sides of a calorimeter
## Footnote
if 2 radicals react, they will form the nonradical and the electron will no longer be bouncing around.
42
free radicals
species with odd numbers (unpaired) electrons
## Footnote
Br, Cl, CH3, CH3CH2
43
homolytic cleavage
when a molecule splits and creates radicals with even numbers of lone electrons
## Footnote
2 Cl atoms being split so they each have 1 e
44
heterolytic cleavage
when the molecule splits and one of the things gets both electrons
45
enthalpy
heat released or absorbed during a rxn at standard conditions
46
entropy
change in randomness, disorder, or freedom of movement
47
relationship between Keq and Q
they are inversely related. if Keq is greater than 1, then G will be negative.
48
what is the trend of stability for radicals and carbocations?
tertiary free radicals are more stable because they want the extra electron. tertiary carbocations are more stable because they have extra positive energy and want the extra electrons.
49
what is the trend of stability for carboanions?
primary carboanions are more stable because they already have extra electrons and are nucleophilic.
50
what is the relative rates of formation for Cl extracting an H atom?
primary- 1
secondary- 3.8
tertiary- 5
this means it is 5 times easier to extract a tertiary hydrogen than a primary one.
51
what is the relative rates of formation for Br extracting an H atom?
primary- 1
secondary- 82
tertiary- 1600
it is 1600 times easier for Br to extract a tertiary hydrogen. however, since there is a bigger energy difference for bromine, that is why it is more selective.
52
