organic chemistry section four lab techniques
Sublime
(of a solid substance) change directly into vapor when heated, typically forming a solid deposit again on cooling
what are the four chemical tests used to identify some functional groups
- I₂ -- for methyl ketone-- - K₂CrO₄/H₂SO₄ - OH - Br₂/ CCl₄ - alkene - IBr/ CCl₄ - unsaturated fats
what are some water sensitive compounds
- acid anhydrides - esters - acid halides -
how do use a chemical test to identify the presence of methyl ketone
- addition of I₂/OH- - this will cause a yellow precipitate to appear
how do you use a chemical test to identify the presence of primary or secondary alcohols and aldehydes
- addition of K₂CrO₄/H₂SO₄ this causes a shift from orange to green
what are the four functional groups that can be identified by common chemical tests that we learn
- methyl ketone - primary and secondary alcohols, aldehydes - alkenes - unsaturated fatty acids
describe the factors that determine the elution time for gas chromotography
- polarity-- the column in any type of chromatography is typically a bit polar - mass-- large molecules move slower
what are the two materials that make up the stationary phase and what is their chemical nature
- silica gel - alumina they are both POLAR
what are the negative ion exchange chromatography things
- sulfonated polystyrene -carboxymethyl-cellulose (CM-cellulose)
what are the three ions used in ion exchange chromatography
-sulfonated polystyrene - carboxymethyl-cellulose - diethylaminoethoxy-cellulose
aniline
AMINE attached to a benzene ring
Azeotrope
An azeotrope or a constant boiling mixture is a mixture of two or more liquids whose proportions cannot be altered by simple distillation. This happens because when an azeotrope is boiled, the vapour has the same proportions of constituents as the unboiled mixture.
how do you use a chemical test to identify the presence of alkenes
Br₂/CCl₄ brown to clear
proteins rich in which amino acids will bind to carboxymethyl-cellulose in the ion exchange column?
Carboxylmethyl cellulose has a negative charge so it will attract the amino acids that are positively charged at neutral pH like arginine, lysine, and histidine
what are the postive ion exchange chromatography ions
DEAE- cellulose diethylaminoethoxy-cellulose
DEAE- cellulose diethylaminoethoxy cellulose
Diethylaminoethyl cellulose (DEAE-C) is a positively charged resin used in ion-exchange chromatography, a type of column chromatography, for the separation and purification of proteins and nucleic acids.
how do you use a chemical test to identify the presence of unsaturated fats
IBr/CCl₄ purple to clear
vapor pressure
It is the partial pressure of its vapor in dynamic equilibrium with its liquid. A substance with a high vapor pressure at normal temperatures is often referred to as volatile. The pressure exhibited by vapor present above a liquid surface is known as vapor pressure. As the temperature of a liquid increases, the kinetic energy of its molecules also increases. As the kinetic energy of the molecules increases, the number of molecules transitioning into a vapor also increases, thereby increasing the vapor pressure.
Rf
RATIO OF FRONTS the distance traveled by the compound of interest/ the distance travelled by the solvent front
Raoult's law
Raoult's law is a law of thermodynamics established by French physicist François-Marie Raoult in 1882. It states that the partial vapor pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component multiplied by its mole fraction in the mixture.
how to remove colored impurities when you want a colorless compound
add activated charcoal-- the colored molecule will be preferentiall bound to the charcoal-- charcoal binds all rganic molecules but becuase of its pi network
what is another name for the stationary phase
adsorbent
why is diethyl ether such a common compound used for acid base extraction?
because it is immiscible in water-- and therefore helps form two llayers
color changes for the reaction of Br₂/ CCl₄ with alkenes
brown to clear
DNPH
dinitrophenylhydrazines
distillation
distillation removes a liquid from another liquid by exploiting their differences in boiling point
ether, amide, phenol, carboxylic acid separation-- which ultimately ends up in the organic layer?
ether
diagnostic tests for which compounds take advantage of dinitrophenylhydrazine (DNPH)
for ketones and aldehydes AND FOR OSAZONE TEST WITH THE SUGARS
fractional distillation
fractional distillation often incorporates glass beads-- which increase the surface area relative to simple distillation-- it is typically used when there is less difference between the vapor pressures of the compounds
GC
gas chromatography
decant
gradually pour (liquid, typically wine or a solution) from one container into another, especially without disturbing the sediment.
color changes for the reaction of K₂CrO₄/H₂SO₄ with primary and secondary alcohols and aldehydes
green to orange
brine solution
in the partitioning of substance into a biphasic solution to emphasize the difference between the aqueous and nonpolar solution-- sometimes the water will have salt ions added to it
how can you identify the best separation solvent
look at the Rf values-- you dont want the greatest additive times-- you want the greatest multiplicative difference
what is the distinguishing physical characteristics of compounds that have been treated with dinitrophenylhydrazine?
melting point differentiates
what is the pKa of a hydrogen bound to a carbon that is alpha to a carbonyl?
pKa of 19
color changes for the reaction of IBr/CCl₄ with unsaturated fatty acids
purple to clear
phenylhydrazine
reacts with ketone and ketone to form a unique structure that amplifies the chemical properties
organic layer
the opposite of the aqueous layer-- non-polar
color change for the reaction of I₂/OH with methyl ketones
yellow precipitate forms
