Ocher Lab 2545
an intensive property is
a property of matter that does not change as the amount of matter changes
azobenzene is
neither an amine nor an organic acid
in order to remove the insoluble solid impurity during your recrystallization, you will perform a _____ using a _____
vacuum filtration, Buchner funnel
rank the intermolecular forces from weakest to strongest ionic, dipole-dipole, van der Waals, hydrogen bonding
van der Waals, dipole-dipole, hydrogen bonding, ionic
melting points are ___ _______ to impurities
very sensitive
True or false: acid-base reactions require both an acid and a base, if an acid is added to an acid, there will be no reaction
True
True or false: the pKa of a protonated cyclohexyl amine is 10.7. at a pH of 2, the amine is still primarily protonated
True
a good separation is achieved when each compound has
a different Rf value
the S,S-isomer and R,R-isomer of the same compound are
a pair of enantiomers
The bronsted-lowry definition of a base is a species that
accepts a proton
the R,S-isomer of a symmetrical molecule is
achiral and meso
pKa is an indicator of the strength of an
acid
the _____ the pH, the lower the hydrogen ion concentration and the ____ acidic the solution
higher, less
when 2 ____ solvents come into contact, they separate into 2 layers according to their densities. The top layer will be ____ dense than the bottom layer.
immiscible, less
________ are intermolecular forces resulting from electron density around one molecule influencing the electron density around another
induced dipole-dipole forces
1-bromobutane and 1-butanol are
irritants and flammable
what letter represents the rate constant?
k
what do you need to assemble a reflux apparatus
large screw cap with a hole, round-bottom flask, stir bar, water condenser, large o-ring
at a pH ___ than the pka, the acidic form dominates
less
qualities of a good recrystallization solvent
low boiling point, nontoxic, inexpensive, inert
to determine which compound will get deprotonated, we look at which compound has the ____ pka
lower
the _____ the pH, the higher the hydrogen ion concentration and ____ acidic the solution
lower, more
when naming alkyl halides, the parent chain is numbered in the direction that gives the substituents the ____ possible numbers, and the substituents are listed in ____ order
lowest, alphabetical
to be chiral, a molecule
may not contain a mirror plane, must be non-superimposable with a mirror image
What intensive properties were measured in lab 2 to identify the solid unknown?
melting point
during lab 5 (addition rxns) you will use _____ to tell which product you obtained
melting point
compounds that contain more than one chiral center and have an internal plane of symmetry are called
meso
alkyl halide reactivity most to least relative (1-4)
methyl, primary, secondary, tertiary
isomers are molecules that have the same ____ but are ____
molecular formula, not identical
reactions involving negatively charged nucleophiles occur _____ rapidly in _____ solvents such as DMSO
more, polar-aprotic
in liquid chromatography, components of a mixture are separated by partitioning between a _____ liquid phase and a solid _____.
moving, adsorbent
Is hexane polar or non polar?
non polar
if you add sodium sulfate to your product and after 5-10 min the solid is clumped, this indicated your sample is ____ and you should_____
not dry, add more sodium sulfate
in an Sn2 reaction the _____ replaces the _____
nucleophile, leaving group
the Sn2 reaction is a ____ -step reaction and the reaction rate depends on the concentration of the _____
one, nucleophile and the electrophile
in an Sn2 reaction, the nucleophile approaches the carbon atom from the ____ side as the leaving group
opposite
generally, extractions involve an ____ phase and an aqueous phase
organic
to name branches alkanes, you should begin by finding the longest carbon chain. this is the ____ chain
parent
the henderson-hasselbalch equation shows the relationship between ____ and _____
pka, pH
using the ABBE refractometer, it is important to
place your liquid sample on the prism with a clean plastic pipette, only turn the dials you are instructed to turn, wipe the glass with a swab of cotton dampened with ethanol
a carbocation is
planar (usually sp2 hybridized)
Is ethyl acetate polar or non polar?
polar
carbocation stability from least to most stable (1-3)
primary, secondary, tertiary
another term for an acid-base reaction is a
proton transfer
TLC is primarily a tool for rapid ______ analysis
qualitative
________ is the purification technique you will use to remove impurities from your solid unknown
recrystallization
The ABBE refractometer measures?
refractive index
Sn1 reactions occur faster or slower in non-polar solvents?
slower
examples of goof TLC techniques
solvent level in the TLC chamber below the spotting line, spot on spotting line should be small, the TLC chamber should be left closed when developing a plate
the hydroxide ion is a _____ base and therefore a ______ leaving group. by protonating the -OH group with the acid catalyst, you can convert it into ____ which is a better leaving group
strong, poor, water
______ bases are better nucleophiles
stronger
the lower the pka the _____ the acid
stronger
the pKa of benzoic acid is 4.17. the pKa of HCl is -7. this means that HCl is a ____ acid than benzoic acid
stronger
What does each letter in the Sn1 reaction stand for?
substitution, nucleophilic, unimolecular
in this reaction what is the acid catalyst?
sulfuric acid
the rate of an Sn1 reaction depends upon the concentration of _____
the alkyl halide
the rate of an Sn2 reaction depends upon the concentration of ______
the alkyl halide and the nucleophile
the rate-determining step of the Sn1 reaction is
the formation of the carbocation
which process directly causes the color change of the reaction indicator in lab 8?
the generation of an acid
In a solvolysis reaction what is the solvent molecule?
the nucleophile
prefixes di-tri, and tetra- are used in naming when
the same group appears more than once
What is TLC used for?
to identify a compound by comparing to a standard, to test the completeness of a reaction, to get a rough estimate of the purity of a product
What is the role of capillary action in TLC?
to move the liquid phase up the plate
in an eclipsed conformation, the forces contributing to the higher energy state include: _____ strain- the repulsion of bonded electrons when the come close to each other -and _____ strain- the repulsion between the electron clouds of atoms or groups of atoms
torsional, steric
True or false: when 2 miscible solvents come into contact, they do not separate into 2 layer
true
during a halogenation reaction, a molecule of bromine adds to an alkene to produce a ______ dihalide, which is a compound with halogens bonded to adjacent carbons
vicinal
all are examples of intensive properties EXCEPT volume, density, boiling point, molecular weight
volume
in general, salts are soluble in ___ and neutral (uncharged) organic molecules are soluble in ___
water, organic solvents
good leaving groups are ____ bases
weak
water is an example of a ____ base, this makes it a ____ leaving group, but a _____ nucleophile
weak, good, poor
_____ bases make the best leaving groups because they are stable in solution as their anions, therefore the _____ the base, the faster it will react as a leaving group
weak, weaker
the stronger the acid the _____ its conjugate base
weaker
How do you tell when the reaction is complete for lab 8?
when the color changes to yellow
Tailing on a TLC plate is?
when the spot has a tail behind it
Bromocresol green at a pH below 3.8 is?
yellow
How to calculate an Rf value?
(it is constant under a set of conditions) calculated by dividing the distance the compound traveled by the distance the solvent traveled Rf = dot/ solvent line
What is a nucleophile?
An electron pair donor (has an available pair of electrons to donate to form a bond)
alkyl branches off of a parent chain are named by replacing the -ane ending with ___
-yl
if the bromination of a symmetrical, cis-alkene proceeded through a sin-addition, (#) different products are formed, the products would be _____
1, a meso-compound
mixed melting point is a technique used to determine the identity of an unknown solid. _____ % of a _______ compound is added to an _______ sample. If it the melting points match there us evidence the compounds are the same.
10, known, unknown
an Sn1 reaction is a ____-step reaction
2
if the bromination of a symmetrical, cis-alkene proceeded through a bromonium ion intermediate, (#) different products are formed, the products would be _____
2, a pair of enatiomers
if the bromination of a symmetrical, cis-alkene proceeded through a carbocation intermediate, (#) different products are formed, the products would be _____
3, a pair or enantiomers and a meso-compound
the pKa of cyclohexyl amine is 10.7. this means that at a pH of 10.7, cyclohexyl amine is
50% protonated and 50% neutral
The oxonium ion has what?
a cross of carbons with an O with 2 H attached to it and a proton on the oxygen
If a compound does not appear visible to the eye, it can be seen if they absorb _____ light. The plates are coated in a ____ chemical and when a plate is exposed to _____, the compounds will appear as _____ spots because they ______ the light.
UV, fluorescent, UV light, dark, absorb
halogenation are _____ reactions
addition
On a TLC plate, less polar substances generally _______ the plate than the more polar substance
advance further up
examples of solid adsorbents used in liquid chromatography
alumina, silica gel, cellulose
m-nitroaniline is a(n)
amine
benzoic acid is
an organic acid
tailing on a TLC plate can result from
application of too much compound on the spotting line, a compound slowly decomposing on the plate
a meso-compound must have
at least 2 chiral centers and a plane of symmetry
in an Sn2 reaction, bond breaking and bond forming are concerted, which means they occur _____
at the same time
What do you return to the stockroom at the end of the unknown lab 2?
automatic pipette
At the end of lab 8 what items will be returned to the stockroom?
automatic pipette and digital timer
____ will deprotonate ____ to form salts of organic acids, these salts are soluble in____
bases, acids, water
in a liquid-liquid extraction an extracting solvent must:
be immiscible with the original solvent, dissolve the solute better than the original solvent
boiling point of the solvent must be ______ (above/below) the melting point of the solid to prevent _____
below, oiling out
Bromocresol green at a pH above 5.4 is?
blue
all techniques used to characterize the alkyl halide product
boiling point, density, beilstein test
in a reflux apparatus water flows in the bottom or the top?
bottom (out through the top)
when naming molecules, ____ are used between numerals, and ____ are used between numerals and letters
commas, hyphens
In an acid-base reaction, the species that has an extra proton in the products is the
conjugate acid (from the base in reactants)
In a acid-base reaction, the species that has one less proton in the products is the
conjugate base (from the acid)
____ isomers- also known as structural isomers- have the same molecular formula but differ in the order that the atoms are attached
constitutional
for the flame test, you drip a ____ wire into your sample, when the wire is heated a ____ flame indicates there is a _____ present
copper, green, halogen
pyridinium tribromide is
corrosive and a lachrymator (irritates eyes and causes tears to flow)
the presence of an impurity will _____ the melting point and _____ the melting point range
decrease, widen
A solid is dissolved in a hot recrystallization solvent. Solubility of the solute (inc/dec). Recrystallization needs to happen (fast/slow ) and is important to make sure _______ is excluded
decreases, slowly, impurities
a molecule containing one chiral center exists as a pair of non-superimposable mirror images, or
enantiomers
melting is an _______ process
endothermic
vaporization is the phase change from liquid to vapor and is an _______ process. Boiling is an example of a _____ change.
endothermic (energy added to system), physical
If a substituent is axial and the structure undergoes a ring flip, the substituent would then be ______
equatorial
True or false: a neutral compound will react with an acid
false
True or false: salts of amines are soluble in organic solvents
false
a chiral carbon is a carbon bonded to ____ different groups
four
Bromocresol green at a pH between 5.4 and 3.8 is?
green
a straight chain alkane with the molecular formula C7H16 is called
heptane
the _____ (higher/lower) the compounds affinity for the solid phase relative to the liquid phase, the slower the compound will move through the adsorbent
higher
the more polar a substance the (higher/lower) it will move on the plate
higher