Organic chemistry Flashcards
How to distinguish enantiomer
Measure the optical activity with a polarimeter
rotate the plane of plane-polarized light in the same extent but in the opposite direction
test for -OH
X MnO4-
correct: Cr2O72-
why substance is soluble in organic solvents
the attractive force between molecules are of similar strength as those in organic solvents
use of aspirin
reduce fever
reduce risk of heart disease
painkiller
reducing inflammation(發炎）
principle of soup
detergent consists of a hydrophobic hydrocarbon tail and a hydrophilic ionic head
hydrophobic tail dissolve in grease
hydrophillic head dissolve in water, reducing surface tension
stirring cause the grease splits to tiny droplets
repulsion of negatively charged head to form emulsion
oil droplets become suspended in aq solution
easy to be carried away by water
observation of esters (2)
two immiscible layers are observed
A fruity smell is detected
which hydrolysis is more favourable
alkaline
acid hydrolysis is reversible but alkaline hydrolysis is irreversible. In alkaline hydrolysis, all reactants are completely converted into products
use of hexanedioic acid in industry
to make nylon 6,6
why hydrocarbon with smaller carbon content is better for a fuel
hydrocarbon with smaller carbon content has a smaller molecular mass and so has a lower boiling point and the molecular size is smaller.
So, it burns more completely.
is soap an ester?
No
there is only COO- ion but no RCOOR
how to convert alkene to alkane
Pass excess H2 to alkene in the presence of Pt
Catalytic hydrogenation
naming
halogen or double bond prioritize?
double bond
why HOOCCH2COOH can form a polymer with H2NCH2NH2 but cannot
HOOCCH2COOH has two COOH grouo to react with NH2 group in the diamine while CH3CH2COOH only has one COOH group
Each HOOCCH2COOH can react with two H2NCH2NH2 to form a chain but CH3CH2COOH cannot
what is aliphatic hydrocarbon
without benzene ring
what is aromatic hydrocarbon
with benzene ring
define isomers in general
isomers are compound having the same molecular formula but different arrangements of atom
what are the two types of isomerism
structural isomerism and stereoisomerism
define structural isomers
structural isomers are compound having the same molecular formula but different structural formula
define stereoisomers
stereoisomers are isomeric compounds having their atoms linked in the same way, but differ in the spatial arrangement of their atoms
why cis-trans isomers exist
it is because of the restricted rotation about a covalent bond
what is a chiral molecule
a chiral molecule is a molecule which is not superimposable on its mirror images. The chiral molecule and its mirror image are called a pair of enantiomers.
what is a chiral carbon
it is a carbon atom which is attached to 4 different atoms or group of atoms
enantiomers have identical chemical properties
T/F
90% correct
exception: enantiomers behave differently when they are reacted with a chiral molecule
enantiomers have identical physical properties
T/F
90% correct (mp bp and density)
except optical activity
density of alkanes compare to water
it is less dense than water
requirement for substitution reaction
UV light or diffused sunlight
direct sunlight should not be used
why cracking has to be carried out in the absence of air
cracking must be carried out in the absence of air because combustion occurs instead of craking in the presence of air
why alkene burns with more soot than an alkane with the same number of C atoms
C:H ratio or percentage by mass of C is higher for the alkene
what is the rule related to addtion reaction of HX
Markovnikov’s rule
the H atom attaches itself to the C atom already carrying the larger no. of H atom
what are the examples of haloalkanes taht are denser than water
CH2Cl2
CHCl3
CCl4
CH3CCl3
other 99% less dense than water in dse
why an alcohol is soluble in water
it has a relatively short carbon chain
formation of H-bond with H2O molecules
when ketone add LiAlH4 then H+
where the H atom is contribute to respectively
LiALH4 that H to 分開 that one
H+ that H to O 隔離 form OH
what are the uses of conc H2SO4 in esterification
catalyst
dehydrating agent in order to shift the eqm position to the right
what is chloroform
trichloromethane
what is acetone
propanone
what is acetic acid
ethanoic acid
what is formaldehyde
methanal
what is isopropyl alcohol
propan-2-ol
why COOH has a more extensive intermolecular H-bonds
as RCOOH has 1 more electronegative O atom than ROH and so there are more lone pair electrons on NOF
which one has a higher bp
H2O2 or H20?
H2O2
as it has more lone pair electrons and thus more extensive H-bonds
acid hydrolysis or acidic hydrolysis
acid hydrolysis!!!!
compare the density of ester with water
usually less dense
so ester float on water when they are not miscible
why alkaline hydrolysis can always goes to completion
its because the RCOOH formed is immediately removed by reaction with OH-
so the eqm position of the first reaction goes to right
first reaction: ester + water to acid + alcohol
what are the smells of amines
amines of lower molecular masses have characteristic ammonia smell while larger amines have fishy smell
how to distinguish ester and amide
heat with NaOH
ester: no observable change at first then 2 layers become miscible
amide: colorless gas bubbles evolved which turn moist pH paper blue (becuz of NH3)
why the yield of most organic reactions are less than 100%
incomplete reaction
side-reactions
presence of impurities in reactants
loss of product during the course of the experiment
what is the use of recrystallization
it is used to purify solid products by removing impurities of different solubilities
what is the requirement in choosing the solvent in recrystallization
the solid product should be dissolved readily in a hot solvent but is much less soluble in the cold solvent
All other impurities must either be insoluble or remain in solution in both cold and hot solvent
it should be volatile so that it is easier to be removed
it should not react with the product
describe the procedure of recrystallisation
a suitable solvent is chosen (which there isn’t any reaction between the solvent and product)
minimum volume of hot solvent is used to dissolve the solid impure product
the mixture is filtered to remove insoluble impurities
the filtrate is allowed to cool slowly so that crystals can reform, with soluble impurities staying in the cold solvent
crystal can be obtained by filtration
what is the consequence for using excess hot solvent to dissolve the impure solid sample during recrystallisation
the product may not seperate out as crystals if too much solvent is used
why the water should be going inside the condenser at the lower point
to ensure the water jacket is fully-filled with water and thus there are better cooling and condensing effect
why the thermometer bulb is level with the side arm during distillation
the temperature of the vapour is measured when it leaves the flask
what is the common name of aspirin
acetylsalicylic acid
define detergents
a detergent is a substance which improves the cleansing ability of water by acting as a wetting agent and an emulsifying agent
what is the source of soapy detergent
hydrolysis of animal fat
what is the source of soapless detergent
they are obtained from a series of reactions of petroleum fractions
what do wetting agents do
it can lower the surface tension of water so that the water can spread over the surface and penetrate into the things and wash away the dirts
what is the other term of alkaline hydrolysis of fat or oil
saponification
how to obtain the soap after saponification
add concentrated NaCl solution to make the soap be less soluble in water
the process is known as salting-out
why concentrated H2SO4 can remove the fat blocking the drain pipes
it can perform acid hydrolysis and form alcohol and acid which can be easily removed by running water
what are the raw materials in manufacturing soapless detergents
- petroleum fractions
- conc. H2SO4
- Conc NaOH
can soapy detergents works well in acidic solution
no
-COO- will form fatty acid with H+ which is insoluble in water
is soapy detergents biodegradable
yes
is soapless detergents biodegradable
not a must
nylon 6,10
6 represents?
10 represents?
6 is for diamine (前者）
10 is for dioic acid（後者）
uses of nylon
ropes
fishing lines
strings for tennis racket
uses of polyesters
water bottle
clothings
definition of addition polymerization
monomer molecules are joined together to form polymer chains without losing any atoms
definition of condensation polymerization
monomer molecules are joined together to form polymer chains with the loss of small molecules
compare the melting point of cis-trans isomers
the melting point of a substance depends on intermolecular attraction as well as molecular symmetry
trans-isomers are more symmetrical in shape and can better fit to solid lattice so it has a higher melting point
why sodium benzoate is more soluble than benzoic acid in water
sodium benzoate is an ionic compound which has stronger interaction with water
while benzoic acid exists as molecules which have weaker intermolecular interactions with water
side effect of aspirin
increase bleeding
stomach upset
