Chapter 2: Functional Groups and Nomenclature Flashcards
what types of atoms are in hydrocarbons
only contain hydrogens and carbons
what are the 2 classifications of hydrocarbons
aliphatic and aromatic
What property about chemical bonding do Lewis models predict?
that electrons have wave properties
what are the two theories of bonding based on the wave of nature electrons
valence bond theory(came first)
molecular orbital theory
in terms of the valence bond model, when can electron pairs be shared
when half-filled orbital of one atom overlaps in phase with half-filled orbital of another
what is constructive interference
is between electron waves of two half-filled atomic orbitals
sigma bond
a bond in which the orbitals overlap along a line connecting the atoms
where do electrons in molecules reside
molecular orbitals (MOs)
where do electrons in an atom resiide
atomic orbitals (AOs)
how are MOs and AOs related
MOs are combinations of AOs, 2 electrons per MO
what combination generates one bonding orbital
additive combination of 2 atomic orbitals
what combination generates an antibonding orbital
subtractive combination of 2 atomic orbitals
symbol for antibonding
sigma star
what is the general formula for alkanes
C(n)H(2n+2)
what is the smallest/most abundant alkane
CH4- (methane)
what are the second smallest and most abundant alkanes
C2H6 (ethane)
C3H8 (propane)
what is natural gas composed of, and what special property do they all have
75% methane
10% ethane
5% propane
(have the lowest boiling points)
boiling point of methane
-160 C
boiling point of ethane
-89 C
boiling point of propane
-42 C
what set of alkanes are gases
C4 and lower
what alkanes are liquid
C4-C8
what alkanes are gases
C9 - C10
what makes alkanes different states of matter at room temp
as you get more carbon atoms, they increase to a warmer state
how many bonds do carbons in methane, ethane and propane have
4 bonds on each carbon
what are the bond angles of carbon in alkanes
109.5
what is interesting about the amount of bonds in carbon compared to normal electron configuration
normally carbon has 2 unfilled orbitals, and because in alkanes it needs 4 bonds, we must use hybridization
who and how did they propose hybridization
Pauling proposed a mixing or hybridization of the s and 3p orbitals to create 4 equal unfilled orbitals called sp3 orbitals
what do all 4 sp3 orbitals have in hybridization
equal energy!
how are 4 hybrid orbitals produced in hybridization
mixing 4 atomic orbitals
in examples such as sp3 hybrid orbitals in methane, why are they better than unhybridized 2s or 2p
they are stronger
sp3 bonding in methane
overlap between partially filled carbon sp3 orbital and partially filled s orbital of hydrogen
(h=1s and C=2sp3)
characteristics of C-C bond in ethane
- like methane, formed by overlap of sp3 on each carbon
- tetrahedral
- 2 half filled sp3 orbitals on each C
- orbitals overlap to form bond
- the electrons on the C’s have opposite spins
- 111 degrees
characteristics of bonding in Ethene
- sp2 because sp3 is not possible (b/c 3 atoms are bonded to each carbon (not 4) so 3 hybrid orbitals form instead of 4)
- planar
- one p orbital is NOT hybridized (hence sp2 not sp3)
- 120 degree angle
sp2 hybrids
2s and 2 2p orbitals are mixed to form 3 sp2 orbitals
- trigonal planar arrangement
- 2p orbitals are 1/2 fill
sigma bonding in ethylene
- form C-H bonds by overlap of sp2 and s
- form C-C bond by overlap of sp2 on each carbon
- all sigma bonds, and unfilled p orbital is on each carbon atom
pi bonding in ethylene
after the C-C sigma bond, there is another C-C bond by the overlap of p orbitals on each carbon
sp hybridization and bonding in ethyne
- linear
- bond angle 180
- 2 half dilled p orbitals, no hybridized
sp hybrid orbitals
the 2s and one of the 2p orbitals are mixed to form 2 sp orbitals
- linear
- 2py and 2pz remain half filled
hybridization of carbon sp3
- 4 atoms
- bond angle = 109.5
hybridization of carbon sp2
- 3 atoms
- bond angles = 120
- one C-C pi bond
hybridization of carbon sp
- 2 atoms
- bond angles = 180
- 2 C-C pi bonds
what does n mean if it is before the name of something
normal, or unbranched
what alkanes have only 1 isomer
CH4
C2H6
C3H8
how many isomers for C4H10 and what type are they
2, constitutional
what are n-alkanes
straight-chain alkanes with general formula
CH3(CH2)nCH3
n-Pentane
is CH3CH2CH2CH2CH3
n-hexane
CH3CH2CH2CH2CH2CH3
can you abbreviate in alkanes
yes
ex)
CH3(CH2)3CH3
what alkanes have 1 isomer
CH4
C2H6
C3H8
what alkane(s) have 2 isomers
C4H10
what alkane(s) have 3 isomers
C5H12
what alkane(s) have 5 isomers
C6H14
what alkane(s) have 9 isomers
C7H16
what alkane(s) have 18 isomers
C8H18
what alkane(s) have 35 isomers
C9H20
what alkane(s) have 75 isomers
C10H22
methane
-1 carbon
CH4
ethane
-2 carbons
C2H6
propane
3 carbons
C3H8
butane
4 carbons
C4H10
pentane
5 carbons
C5H12
hexane
6 carbons
C6H14
heptane
7 carbons
C7H16
octane
8 carbons
C8H18
nonane
9 carbons
C9H20
decane
10 carbons
C10H22
undecane
11 carbons
CH3(CH2)9CH3
dodecane
12 carbons
CH3(CH2)10CH3
tridecane
13 carbons
CH3(CH2)11CH3
tetradecane
14 carbons
CH3(CH2)12CH3
pentadecane
15 carbons
CH3(CH2)13CH3
hexadecane
16 carbons
CH3(CH2)14CH3
heptadecane
17 carbons
CH3(CH2)15CH3
octadecane
18 carbons
CH3(CH2)16CH3
nonadecane
19 carbons
CH3(CH2)17CH3
Icosane
20 carbons
CH3(CH2)18CH3
methyl
CH3
methyline
CH2
Methine
CH
what are alkyl groups
substituents derived from alkanes (they lack 1 hydrogen at the point of attachment)
ex)
CH3CH2CH2CH2
what are the classifications of carbon atoms
primary
secondary
tertiary
quaternary
what type of carbon classification is easiest and most difficult to react with
easiest = primary hardest = tertiary
more carbon = harder
how to label when substituents with 2 branches in addition to others are there
make sure that the first double branch is the lowest number (label “backwards” if needed)
general formula for cycloalkanes
CnH2n
how many degrees of unsaturation are assigned to each saturated ring in cycloalkanes
1 degree of unsaturation for structural purposes
common name for 2-methylpropyl
isobutyl
common name for 1-methylpropyl
sec-butyl
common name for 1,1-dimethylthyl
tert-butyl
how do you do naming when you have 2 or more substituents to name
put them in alphabetical order, but ignore the prefix (such as di or tri) when alphabetizing
naming substituted cycloalkanes
same as naming branched alkanes BUT
if there is only 1 substituent, DO NOT LABEL WITH A 1 !!
what happens if the cycloalkane ring has fewer carbons than the substituent does?
the ring becomes the substituent, and the substituent becomes the parent
what is petroleum and how many hydrocarbons does it have
a liquid micture
150 hydrocarbons (half are alkanes or cycloalkanes)
what is cracking (thermal and catalysts)
cleaving carbon-carbon bonds in heavy alkanes
heat=thermal
catalysts = catalytic
what is reforming
converts hydrocarbons in petroleum to aromatic, and highly branched alkanes because they are better automotive fuels than unbranched alkanes/cycloalkanes
what factor in the liquid phase will affect the boiling point of that liquid
the attractive forces (van der waals forces)
what are the 3 types of vander waal forces
- dipole dipole (includes hydrogen bonding)
- induced dipole dipole
- induced dipole induced dipole
what type of bond do alkanes have and why
temporary induced dipole induced dipole
because alkanes have no strong dipoles
what type of alkanes have more induced dipole induced dipole interactions
long chain alkanes
what is the relationship between carbon chain length and boiling point
the longer the chain, the higher the boiling point (needs more NG to move to the next phase)
what is the relationship between boiling point and molecular weight in unbranched (n) alkanes
boiling point will increase as molecular weight increases
why do branched alkanes have a lower boiling point than unbranched
because they have a lower surface area and this a lower boiling point
what does it mean when we say that solid n-alkanes are soft low melting solids
the same intermolecular forces hold the molecules together in the solid state
solubility of alkanes in water
alkanes and all hydrocarbons are basically insoluble in water and hydrophobic
do alkanes float or sink
float
what is the acidity of alkanes and cycloalkanes like
they are like hydrocarbons and very weak
they have the lowest pKa in hydrocarbons
what type of hybridization is most and least acidic for hydrocarbons
sp = most acidic sp3 = least acidic
combustion of hydrocarbons
hydrocarbon + O2 = Co2 + H2O
exothermic
how many molecules of CO2 and how many molecules of H2O does combustion of isomers C8H18 create
8 CO2
9 H2O
YET DIFFERENT AMOUNTS OF ENERGY
what is the relationship between the different amounts of energy in combustion of isomers compared to relative energies of isomers
because the energy of combusion is different, this signals that the relative energyies of isomers must be different too
what is the relationship between energy released and stability of isomers
least stable isomers will have the highest energy
the most stable isomers will have the least energy released
how can you calculate the oxidation state of CHO’s
H = +1 O = -2
then you can calculate C
what does the total sum of the oxidation states of all atoms in any given species equal
the net charge on that species
what is the oxidation number for group 1A metals
+1
what is the oxidation number for group 2A metals
+2
what is the oxidation number for group 3A
-3
what is the oxidation state of group 6A
-2
what is the oxidation state of group 7A
-1
what is the oxidation state of C in CH3Cl and CH3OH
-2
what is the oxidation state of C in CH4 and CH3Li
-4
what does the oxidation of carbon correspond to
an increase in bonds between C and O
a decrease in the number of H-O bonds
what does reduction correspond to
an increase in C-H bonds
a decrease in C-O bonds
in general, what does increasing the oxidation state of carbon do
it decreases the hydrogen content
