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organic chemistry Flashcards

1
Q

What is a primary alcohol

A

the carbon the OH is bonded to is attached to one carbon (secondary - 2)(tertiary - 3)

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2
Q

Which alcohols are soluble

A

C1 - C3 (soluble due to H bond with OH), as the chain length increases more hydrophobic properties are introduced, decreasing solubility

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3
Q

Why do alcohols have relatively high boiling points

A

hydrogen bonding in the OH, so more OH groups the higher the BP

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4
Q

Why does a longer chain have a higher boiling point

A

larger molecule so has stronger forces

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5
Q

How is glycerol made and what are its uses

A

by product of soap and biodiesel manufacture. Used as moisturiser, sweetener etc…

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6
Q

1,2 ethandiol uses and hazards

A

antifreeze. Ingestion can lead to death by alcohol dehydrogenase, to treat add ethanol

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7
Q

Oxidation of alcohols

A

primary alcohol - aldehyde then carboxylic acid. Secondary alcohol - ketone. Tertiary does not oxidise.

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8
Q

Alcohols acting as an acid

A

the longer the chain, the weaker the acid. Reacts with alkali metals to release hydrogen and an anion (alkoxide)

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9
Q

What are alkoxides

A

strong bases that are used in organic synthesis when strong base required in non aqueous solution

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10
Q

How can alcohols act as a base

A

in the presence of a strong acid by accepting a proton to form an oxonium ion

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11
Q

What reactions do primary oxonium ions undergo

A

do not lose water to form primary carbocations (too unstable) so undergo elimination or can be directly attacked by nucleophiles (SN2)

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12
Q

What is the ether functional group

A

R-O-R

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13
Q

Ether as a polar molecule

A

More polar than alkanes due to the presence of oxygen but less than alcohols as there is no hydrogen attached to the oxygen

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14
Q

Hydrogen bonding in ether molecules

A

exists between water and ether but not between ether molecules

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15
Q

Chemical features of ethers

A

little reactivity so are normally used as solvents. Has a low boiling point

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16
Q

How to name an ether

A

For the shorter hydrocarbon chain, change -yl to -oxy

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17
Q

Hydrogen bonding in amines

A

exists between amines and water

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18
Q

What is a homologous series

A

successive compounds that differ by CnH2n

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19
Q

Where do alkanes appear in biology

A

animal pheromones, plant waxy cuticle and floral scents

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20
Q

What is an alkane

A

straight or branched hydrocarbons with only single covalent bonds between the carbons

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21
Q

What is an isomer

A

when 2 molecules have the same molecular formula but different 3D structure

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22
Q

What is a constitutional (structural) isomer

A

when molecular formulas are the same but arrangements of atoms differ

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23
Q

Why do branched alkanes have a lower boiling point

A

because they have a smaller surface area so don’t pack as well together, leading to fewer intermolecular interactions

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24
Q

What is free rotation

A

occurs around single bonds so alkanes are constantly moving. Creates conformation isomers

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25
What is an eclipsed conformation isomer
When 2 of the atoms are closer together
26
What is a staggered conformational isomer
Atoms are the furthest away from each other
27
What is conformational isomerization
stereoisomerisation where isomers are formed by rotating around a single bond
28
Combustion of alkanes
results in CO2 and H2O
29
Cracking of alkanes
Breakdown of larger alkanes into smaller alkanes (smaller molecules are more useful)
30
dehydrogenation of alkanes
removal of H2 from an unsaturated hydrocarbon
31
Halogenation of alkanes
replacing a hydrogen with a halogen (free radical substitution - homolytic fission)
32
Which carbon is the most reactive
tertiary is the most then secondary and primary is the least reactive
33
Radicals being stabalized by hyperconjugation
As the radical forms the carbon center transforms from sp3 hybidized into sp2 hybridized. Delocalization of the bonding electrons from carbon next door by overlap with partly filled p orbital. Net stabilizing effect (less energy required to generate the radicals)
34
How many bonding pairs do primary, secondary and tertiary carbons need to stabalize
primary - 1, secondary - 2, tertiary - 3. Tertiary is the most stable (electron transducing effect)
35
What is the bonding in alkenes
sigma bond (sp2 from hybridisation) pi bond (overlap of p orbitals)
36
What is a constitutional (structural) isomer
same molecular formula but different binding patterns and atomic organisations
37
What is a geometric isomer
atoms arranged in the same order, but spatial arrangement differs
38
What is a Z isomer
2 groups with highest priorities are on the same side
39
What is an E isomer
2 groups with highest priorities are on opposite side
40
What causes geometric isomers not to occur
if 2 identical groups are attached to the carbon
41
cis/trans isomers in vision
11-cis-retinal derived from vitamin A combines with proteins (opsins) to form visual pigment Rhodopsin. Conversion triggers a cascade of events the brain interprets as seeing
42
cis/trans isomers and fatty acids
most natural fatty acids are cis isomers, during cooking converted to trans isomers. Trans fatty acids can disrupt normal fatty acid processing increasing risk of stroke and heart attack
43
Reactivity of double bonds
pi bond creates a high electron density above and below C=C making them suseptible to electrophillic attack. Alkenes act as nucleophiles
44
Alkene reactions
Electrophillic addition, hydorgenation, hydration and hydrohalogenation
45
What are alkynes
have a carbon to carbon triple bond
46
What is Markovnikov's rule
the route that makes the most stable carbocation is favoured and produces the major product
47
What is syn addition
addition of two substituents to the same side of an unsaturated molecule
48
What is anti addition
e addition of two substituents to opposite sides of an unsaturated molecule
49
What are cycloalkanes
sp3 hybridised carbons and are therefore not planar. They have restricted rotation of C-C bonds in cyclic structures leading to conformational isomers
50
What is a resonance structure
alternative single and double bonds
51
Describe the structure of benzene
sp2 hybridised and is planar. Contains 6 electrons in pure p orbitals that are capable of overlapping. Electrons are delocalised around the ring and electrons both above and below are very stable
52
Benzene reactions
electrophillic substitution. Delocalised electrons exposed above and below the plane of the molecule which is attractive to electrophiles (which must be very polarised)
53
How can halogens become reactive enough to react with benzene
using Lewis acids e.g., AlX3
54
What are activating side groups
electron donating so ring is more electron rich and substitution occurs at a faster rate e.g. OH. Take ortho or para positions
55
What are deactivating side groups
electron withdrawing groups, ring becomes electron poor, substitution occurs at a slower rate e.g., COOH. Takes meta position
56
Forces in carboxylic acids
hydrogen bonds on the OH but the rest of the molecule has london forces
57
Properties of carboxylic acids
longer hydrocarbon, less soluble. Exist as dimers. High BP (due to H bonds)
58
How can carboxylic acids act as an acid and a base
double bonded O can accept a proton (base). H from OH can be lost (acid)
59
The effect of chain length on acidic properties of the carboxylic acid
longer the chain the weaker the acid (higher pKa), because alkyl groups push electron groups away causing an extra build up of negative charge on COO- making it less stable
60
What is a carboxylate ion
has a negative charge which becomes delocalised between the 2 oxygen molecules
61
Formation of an ester
carboxylic acid + alcohol. Catalysed by conc H2SO4/ HCl
62
How to name an ester
yl (from alcohol). anoate (from carboxylic acid)
63
Acid hydrolysis of an ester
alcohol + carboxylic acid
64
Alkali hydrolysis of an ester
alcohol + carboxylate ion
65
How are amides made
carboxylic acid + ammonia/amine via a condensation reaction
66
What is a lactam
a cyclic amide. Constituent parts of some antibiotics like penicillin
67
Electronegativity of halides
F, Cl and Br are more electronegative so the C- halogen bond is polar (unequal distribution of electrons)
68
Why is F the most electronegative
most protons in the nucleus, and the valence electrons are the closest to the nucleus
69
What is an optical isomer
have a chiral centre that creates non superimposable mirror images
70
When is a carbon compound a chiral centre
if at least one carbon is bonded to 4 different atoms or groups
71
What is achiral
doesn't have 4 different atoms bonded to the carbon
72
What are enantiomers
pairs of chiral molecule
73
What is the +/- system for distinguishing between enantiomers
based on rotation for polarised light
74
What is the R/S system for distinguishing between enantiomers
describes configuration of groups around a chiral
75
What is the D/L system for distinguishing between enantiomers
D - hydroxy group on the right side. L - hydroxy group on the left side
76
R and S system on distinguishing between enantiomers
Identify stereogenic (chiral) centre Assign priority number to each group (higher atomic number is given higher priority. If 2 are the same asses the atoms that are attached to those atoms) Arrange so lowest priority group is pointing away Follow 1-2-3 around circle (if u look clockwise label ‘R’, anti-clockwise label ‘S’)
77
What does rate of halogen reactions depend on
[nucleophile] and [carbon skeleton]
78
Reactions of halogens
involved in both nucleophillic and electrophillic reactions
79
If a stable halogen compound is formed what reaction mechanism was most likely used
SN1
80
What influences carbocation stability
number of substituents and accessibility of carbon and nucleophile attack
81
What are sigma bonds
end to end overlap of orbitals as atoms approach. Electrons of one atom are attracted to nucleus of the other. Continues until repulsion between the nuclei outweighs this attraction
82
Bonding of carbon
has 2 unpaired electrons. Needs to be hybridisation of atomic orbitals. Forms 4 bonds
83
Sp3 hybridisation
Methane has 4 bonds that are identical in length and have a bind angle of 109.5 Promoting a 2s electron into an empty 2p orbital gives 4 unpaired electrons. (2s1, 2p3) But methane would have 4 bonds, 3 are the same and one would have a different length when they need to be the same All 4 bonds in methane are equal length so atomic orbitals involved in the bind are equivalent S and p orbitals are mixed to form hybrid orbitals One s and 3 p orbitals are mixed so sp3 hybridisation
84
sp2 hybridisation
Carbon only bonded to 3 atoms Ethene: planar molecule with bond angle of 121.3 degrees A 2s electron is promoted So one s and 2 p orbitals hybridise together These 3 hybrid orbitals can form one s bond each (one p orbital left over) Bond angle of 121.3 degrees The 2 pure p orbitals left over, overlap sideways to form a pi bond.
85
sp hybridisation
E.g. ethyne Hybridise one s and one p orbital to make 2 sp orbitals 2 pure p orbitals are ;eft over per carbon so they sideways overlap to form 2 pi bonds Each carbon forms 2 sigma and 2 pi bonds
86
What is homolytic cleavage
1 electron to each atoms, formation of radicals
87
what is heterolytic cleavage
2 electrons transferred, formation of ion

Biological Chemistry (12 decks)

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