Chem
Sesquiterpenes
" sesqui means ½ " *contain 3 isoprene units
Gabriel Synthesis
- An amino acid is generated from phthalimide (nucleophile) and diethyl bromomalonate, using two SN2 reactions, hydrolysis, and decarboxylation. phthalimide = big molecule !
Effect of a catalyst
-A catalyst has no effect on the equilibrium composition -It increases the rate of both the forward and reverse reaction to the same extent -While equilibrium composition and concentration do not change, equilibrium is reached in a shorter time
What can you do to increase the rate of the reaction ?
-increase concentration (3% - 30% [cocaine]): increase frequency of collisions (A) -increase Temp (not some biological): increase number of collisions... greater than Ea inhibitors DECREASE rate of the reaction
Terpenes
-metabolic precursors to steroids and other lipid signaling molecules -odiferous chemicals -class of lipids built from isoprene - carbons are grouped in multiples of 5 -grouped according to the # of isoprene units present -a single terpene consists of 2 isoprene units
The graph shows the changes in concentration during the formation of HI(g) from a mixture of H2(g) and I2(g). If the measurement is taken at equilibrium, how many moles of HI(g) are present in a 750 mL sample of the reaction mixture? (NOTE: HI(g) is at 6M concentration) A.0.8 mol B.1.9 mol C.4.5 mol D.6.0 mol
0.75L x 6mol/L = 4.5 mol --> C.
electron capture
0/-1 e on reactant side So what you see is -1 atomic number
exceptions to the Aufbaf Principle
1. Unpaired electrons are more stable 2. Half-filled subshells are most stable 3. Completely filled subshells are more stable than unevenly filled subshells ex. Group 6 - Cr: [Ar]4s^2, 3d^4 --> 4s^1, 3d^5 Group 6 - Cu: [Ar]4s^2, 3d^9 --> 4s^1, 3d^10
IR spec for a amide ?
1690-1650 cm-1
IR spec for a carboxylic acid ?
1725-1700 cm-1
IR spec for a ester, aldehyde and ketone ?
1750-1735 cm-1 ester 1740-1720 cm-1 aldehyde 1725-1705 cm-1 ketone
Tetrahedral(bent)
2 bonds, 2 lone pairs (type of sp3 hybrid) or.. 2 bonds, 1 lone pair (type of sp2 hybrid)
Isoprene
2-methyl-1,3-butadiene C5H8
thin layer chromatography
Stationary phase - polar Mobile phase - nonpolar Thin-layer chromatography (TLC) is a technique used to evaluate a compound's purity. The components of a mixture are separated based on polarity, and a single spot on a TLC plate is indicative of a compound's purity.
Streker Synthesis
Take an aldehyde with an R group. Add cyanide and ammonia. Now you have an amino group, R group and cyanide group. Replace the nitrogen from cyanide with water to make carboxylic acid. Tada, it's an amino acid with an R group.
IR (functional groups to know)
O-H =3200-3600 cm^-1 C=O - 1700 cm^-1 C=C - 1650 cm^-1 C≡C , C≡N - 2100-2260 cm6-1
Gay-Lussac's Law
P1/T1=P2/T2 (directly proportional)
Boyle's Law
P1V1=P2V2 (inversely proportional) as pressure increases, volume decreases (vice versa)
Assume that helium behaves as an ideal gas. What is the estimated density of 1.0 g of helium gas at a temperature of 27 °C and a pressure of 3.0 atm? (Note: Use R = 0.0821 L∙atm∙mol−1∙K−1) A.1.3 × 10−4 g/mL B.5.0 × 10−4 g/mL C.1.0 × 10−3 g/mL D.1.4 × 10−3 g/mL
PV= nRT -ideal gas law if mass and volume of the gas sample is know we can calculate density: p=mass/Vol (SI: g/mL) In this question we dont know the volume which the gas occupies so we cant find the density. Fist find mol of He: 1.0 g x 1mol/4g = 0.25 mol He Now we use ideal gas law formula to calculate the Volume gas occupies: V= nRT/P = (0.25mol)(0.0821)(300K)/(3atm) = 2L ~~> 2000mL NOW! we can use the density formula to find the density of the gas under given conditions: p=mass/Vol = 1g/2000mL = 5.0 × 10−4 g/mL
Rf value equation
RF= solute/ solvent
Effect of temperature on Keq
Rxn type: exothermic ... adding heat decrease Keq (form more reactants) -opposite if heat is removed Rxn type: endothermic ... adding heat increase Keq (form more products) -opposite if heat is removed
vacuum distillation
appropriate for compounds that have boiling points >150°C, which may decompose when heated beyond this temperature. To avoid decomposition, the distillation apparatus is connected to a vacuum, decreasing the pressure of the system and consequently lowering the boiling points of the mixture components. Neither chloroform nor benzene has a boiling point >150°C
the y-intercept of a line in y=mx+b
b
Monoterpenes
contain 2 isoprene units
triterpenes
contain 6 isoprene units, can be converted to cholesterol and various steroids
If alcohol was to undergo substitution reaction, which of the following would improve alcohols leaving group ability?
conversion of alcohol to mesolate/tosylate (stabilize neg charges) -they make alcohols a good LG ! Substitution reactions require strong nucleophiles and electrophiles and good leaving groups. When a nucleophile attacks an electrophile, a bond is formed between the nucleophile and electrophile whereas the bond between the electrophile and the leaving group is broken. A leaving group containing an electron withdrawing group can enhance the partial positive charge of the electrophile. Leaving groups are weak bases and are able to accept electrons; they often can be stabilized by the delocalization of electrons through resonance and an inductive effect.
how are isoprene unites combined ?
head-head head-tail tail-tail
Ketoses such as fructose are expected to give positive Tollen's test because ___.
ketoses tautomerize to aldoses
phase diagram of water
liquid to solid- freezing liquid to gas- vaporization gas to solid - deposition solid to gas- sublimation gas to liquid - condensation
the slope of a line in y=mx+b
m
determining delta H from the slope
negative slope = (+)deltaH positive slope = (-)deltaH
determine signs of enthalpy and activation energy of exergonic reaction ?
negative, because ΔH = Hf - Hi = (-) --- because the products are lower in energy than the reactants (it would be positive if it was endergonic) Activation energy is positive because the transition state is higher than reactants.
When ΔS° is negative and ΔH° is positive, the process _______.
not spontaneous (+ΔG°) at any temperature.
sp3 hybridization
tetrahedral, 109.5 degrees
effective nuclear charge (Zeff)
the actual nuclear charge experienced by an electron, defined as the charge of the nucleus plus the charge of the shielding electrons Zeff = #protons - #nonvalence electrons = Na: 11-10 = 1 = Mg: 12-10 = 2 = Cl: 17-10= 7
Tetrahedral(trigonal pyramidal)
3 bonds, 1 lone pair (type of sp3 hybrid)
trigonal bipyramidal(t-shaped)
3 bonds, 2 lone pairs (type of dsp3 hybrid)
Convert 30 mL of Eth to molecules (MM= 46.08 g/mol)
3.1x10^23 molecules
IR spec for a carboxylic acid OH group?
3000-2500 cm-1
IR spec for a amines ?
3600-3200 cm-1
trigonal bipyramidal(see-saw)
4 bonds, 1 lone pair (type of dsp3 hybrid)
octahedral, square planar
4 bonds, 2 lone pairs
diterpene
4 isoprene units
alpha decay
4/2 He
octahedral, square pyramidal
5 bonds, 1 lone pair
Tetraterpenes
8 isoprene units (remember 1 isoprene = C5H8)
During distillation, superheating of the reaction mixture should be avoided. Which of the following would prevent superheating? A.Adding boiling chips to the distillation flask B.Increasing the rate at which the distillation flask is heated C.Using cold water in the condenser D.Heating the distillation flask under reduced pressure
A.Adding boiling chips to the distillation flask Superheating occurs when a liquid is heated above its boiling point but does not boil. Surface tension can cause superheating because it can inhibit the formation of bubbles. As bubbles attempt to form, surface tension causes a local increase in vapor pressure that surpasses the ambient pressure, allowing the liquid to heat beyond its boiling point. This phenomenon can cause the formation of large bubbles at the surface, which can erupt violently and eject the hot liquid from the distillation flask in a process called bumping. This effect is difficult to overcome without scratches or crevices in the container where smaller bubbles can begin to form. Boiling chips are made of nonreactive porous material and provide nucleation sites where small bubbles of vapor can form. This effect overcomes the surface tension and allows the liquid to boil evenly at its normal boiling temperature, thereby preventing superheating.
Which of the following molecules is unable to form hydrogen bonding with water ? A.C2H4Br2(77%) B.C3H9N(2%) C.C9H18O2(1%) D.C2F4(18%)
A.C2H4Br2(77%) Hydrogen bonding is a strong intermolecular force that occurs between a hydrogen atom on one molecule and an electronegative atom with a lone electron pair on another molecule. The hydrogen atom is the bond donor and must be covalently attached to a small electronegative atom that withdraws electrons from hydrogen, giving it a partial positive charge. The partial positive charge is then attracted to the partial negative charge of the lone pair of electrons in the bond acceptor. These interactions can only occur over short distances, so they require sufficiently small electronegative atoms in both the donor and acceptor molecules, and are essentially limited to fluorine, nitrogen, and oxygen.
A solution of Compound 1, shown below, absorbs light maximally at 448 nm in the absence of copper(II) ions but shifts to a 623 nm absorption maximum upon the addition of Cu2+. Which of the following best describes this process? A.Changes in electronic structure cause the solution to change from yellow to blue. B.Changes in vibrational modes cause the solution to change from green to yellow. C.Changes in the mass-to-charge ratio (m/z) cause the solution to change from violet to orange. D.Changes in nuclear spin cause the solution to change from colorless to violet.
A.Changes in electronic structure cause the solution to change from yellow to blue. In general, the perceived color of a substance is complementary to the color of the wavelength that is maximally absorbed by that substance. For example, a molecule that absorbs blue light will appear orange and vice versa. When the basic colors of the visible spectrum (red, orange, yellow, green, blue, and violet, or ROYGBV) are arranged in a wheel with red and violet next to each other, a color's complement is the color directly across from it on the wheel. According to the given information, Compound 1 absorbs violet light (448 nm), so it appears yellow (complement of violet). After Cu2+ is added, the absorption maximum changes to 623 nm and the compound absorbs orange light, causing it to appear blue (complement of orange). Therefore, upon the addition of Cu2+, Compound 1 must undergo a change in electronic structure that causes the solution to change from yellow to blue.
When oxalate anions, C2O42−, are added to a solution of [Fe(H2O)6]3+, the formation of [Fe(C2O4)3]3− occurs in a series of steps that together result in the following overall reaction: [Fe(H2O)6]3+(aq) + 3 C2O42−(aq) → [Fe(C2O4)3]3−(aq) + 6 H2O(l) During the first step of the reaction, two new coordinate bonds are formed to produce an intermediate ion of: A.[Fe(H2O)4(C2O4)]+(aq). B.[Fe(H2O)2(C2O4)2]−(aq). C.[Fe(C2O4)3]3−(aq). D.[Fe(H2O)5(C2O4)]2−(aq).
ANSWER: A In the [Fe(H2O)6]3+ complex ion, an uncharged water molecule serving as a ligand is a weak Lewis base and can be displaced by the oxalate (C2O42−) anion, a stronger Lewis base. Each C2O42− anion displaces two water molecules and decreases the overall charge of the resulting complex ion by −2. Displacement of water within the complex occurs in a stepwise sequence. In the first step, two water molecules are displaced from [Fe(H2O)6]3+ by a single C2O42− anion to form an intermediate complex ion: [Fe(H2O)6]3+(aq) + C2O4 2−(aq) → [Fe(H2O)4(C2O4)]+(aq) + 2 H2O(l) In the second and third steps, additional C2O42− anions displace the remaining water ligands to form the final product. (Choice B) This is the intermediate ion formed during the second step of the reaction, not the first step. (Choice C) This is not an intermediate ion; it is the end product formed during the final third step of the overall net reaction. (Choice D) Both the ion charge and this formula are incorrect. The first step adds one C2O4 2− ion to the complex, but each oxalate ion displaces two water molecules and decreases the overall charge of the complex by −2.
aldol condensation
Aldehyde + Aldehyde Ketone + Ketone Aldehyde + Ketone An aldol condensation requires two carbonyl groups (from ketones and/or aldehydes), and these may be from separate molecules or within the same molecule. - - The reaction begins with deprotonation of an α-carbon (carbon adjacent to a carbonyl) to form an enolate. - Next, the nucleophilic enolate attacks another carbonyl, forming a new carbon-carbon bond (the aldol product), in which the carbonyl adjacent to the nucleophile remains intact. - Finally, -OH elimination takes place to give an α,β-unsaturated enone. A reaction between two separate compounds results in the addition of one compound to the other, whereas an intramolecular reaction within the same molecule (as in a diketone) results in a cyclization.
why do we use experimental controls ?
An experimental control is a measurement taken with all experimental conditions in place except the independent variables. The dependent variables are unknown values measured and analyzed in relation to the independent variable. The control setup allows for baseline measurements of dependent variables in the absence of independent variables, allowing for a more accurate assessment of the independent variables' effects.
An ideal gas has 4 characteristics:
An ideal gas has 4 characteristics: 1. An ideal gas has no attractive or repulsive forces between the gas molecules 2. The size (molecular volume) of the individual gas molecules of an ideal gas is negligible (taken to be zero) compared to the volume (space) of the container the gas occupies 3. Collisions between the molecules of an ideal gas are completely elastic (no energy is lost by interactions or friction) 4. Ideal gas molecules have an average kinetic energy (energy of motion) that is directly proportional to the gas temperature.
If a naturally occurring sample of an unidentified element is found to contain three isotopes (A, B, and C) and consists of 90.5% isotope A (mass number 20), 0.3% isotope B (mass number 21), and 9.2% isotope C (mass number 22), the atomic weight of the element measured from the sample will be: A.greater than 21 amu.(10%) B.less than 21 amu.(79%) C.equal to 21 amu.(8%) D.unrelated to the amount of isotope B.(1%)
Answer: less than 21 amu
When the platinum-based engine is run continuously at 300 K for 1 hour with 0.5 atm of H2 and 0.5 atm of O2 injected for each reaction, approximately what mass of water will be produced? A. 0.36 g B. 6.5 g C. 360 g D. 6,500 g
B. 6.5 g If the reaction proceeds for 1 hour, it will produce: 6 mmol/min × 60 min = 360 mmol of water To determine the mass of water produced, the molar amount must be multiplied by the molecular weight. Water has a molecular weight of 18 g/mol, or 18 mg/mmol: 360 mmol × 18 mg/mmol = 6,480 mg For the final answer, convert to grams: 6,480 mg × 1 g/1,000 mg = 6.48 g ≈ 6.5 g
calculate theoretical yield of Calcium citrate(MW: 500ng/nmol) if 15nmol of potassium citrate and 15nmol of calcium oxalate are mixed. CaC2O4 + K3C6H5O7 --> Ca3(C6H5O7) + K2C2O4
Balance first: 3CaC2O4 + 2K3C6H5O7 --> Ca3(C6H5O7) + 3K2C2O4 Now notice that it isnt 1:1 ratio so you need to find the limiting reagent since the amount of product made will be dependent on limiting reagent. 15nmol CaC2O4 * 1/3nmol = 5 nmol Ca3(C6H5O7)2 15nmol K3C6H5O7 * 1/2nmol = 7.5 nmol Ca3(C6H5O7)2 Now convert to ng 5 nmol * 500ng/nmol = 2500ng Ca3(C6H5O7)2
Which gas would occupy more volume at a constant temperature and pressure, 1.5 g of N2 gas or 1.5 g of O2 gas?
Because the masses of both N2 and O2 are equal (1.5 g each), the gas with the lower molar mass has more molecules. Using the periodic table, the molar mass of N2 is calculated to be 28 g/mol, and the molar mass of O2 is 32 g/mol. Therefore, the N2 gas has more moles and occupies a larger volume. So, N2 occupy more volume because it has more moles.
Which element undergoes change in oxidation state corresponding to a loss of two electrons 5 Cl−(aq) + 2 MnO4−(aq) + 11 H+(aq) → 2 Mn2+(aq) + 5 HClO(aq) + 3 H2O(l) A. Mn B. O C. Cl D. H
C. Cl 5Cl- --> 5HClO -1 ------> +1 So 2e lost 2MnO4- ---> 2Mn2+ +7 ------> +2 So 5e lost
Polarity of organic compounds: Carboxylic acid > Amide > ___ > ___ > ___ > ___ > Ether > Alkane
Carboxylic acid > Amide > Alcohol > Amine > Ketone then aldehyde > Ester > Ether > Alkane
Characteristic functional group absorptions include: _____ cm−1 (O-H stretch) _____ cm−1 (sp C-H stretch) _____ cm−1 (sp2 C-H stretch) _____ cm−1 (sp3 C-H stretch) _____ cm−1 (C=O stretch)
Characteristic functional group absorptions include: 3650-3200 cm−1 (O-H stretch) 3300 cm−1 (sp C-H stretch) 3100 cm−1 (sp2 C-H stretch) 3000 cm−1 (sp3 C-H stretch) 1810-1650 cm−1 (C=O stretch)
A 0.040 M HCl solution is measured in the laboratory and has an osmotic pressure of 1.9 atm. What is the estimated osmotic pressure of gastric acid (approximated as 0.10 M HCl) under the same conditions? A.0.19 atm B.0.40 atm C.2.4 atm D.4.8 atm
D. 4.8 atm
Which compound has the bond with the smallest dipole moment? A.H2O B.H2S C.H2Se D.H2Te
D.H2Te
B- decay
Daughter atom: Atomic # +1 (electron emission)
B+ decay
Daughter atom: Atomic # -1 (positron emission)
High Performance Liquid Chromatography (HPLC)
High-performance liquid chromatography (HPLC) is a purification method that separates mixtures based on the component's affinity for the stationary phase. Compounds that have an affinity for a column interact with the stationary phase and will be retained on the column for a longer time than those that do not have an affinity for the column. Chiral columns have a higher affinity for one configuration of a stereocenter than the other. A standard can be used to optimize conditions for the purification and to predict the retention time of a known compound.
Equivalent protons
Hydrogen atoms bonded to the same atoms that therefore experience the same magnetic field in the NMR spectrometer Compound (in the picture) contains four aromatic hydrogen atoms (Ha-Hd). Ha and Hd are chemically equivalent because they are both adjacent to an aromatic C-NO2 and an aromatic C-H, which is adjacent to an aromatic carbon with a side chain. Similarly, Hb and Hc are equivalent, being adjacent to identical chemical groups. Because there are two sets of equivalent aromatic hydrogen atoms and no other aromatic protons, there are two aromatic hydrogen signals in the 1H NMR spectrum.
osmotic pressure equation
II=iMRT i: # of particles in solution M: molarity R: gas constant T: tempt in Kelvins
Bohr model of the atom
In the Bohr model of the atom, several assumptions are made regarding electrons and their locations around the nucleus. The Bohr model asserts that: 1. Electrons move around the nucleus in fixed circular orbits, which are only allowed at particular intervals from the nucleus. 2. Electrons in orbits farther from the nucleus have higher energy than electrons in orbits closer to the nucleus. 3. Energy is absorbed by an electron moving from a lower orbit to a higher orbit, but energy is emitted by an electron returning from a higher orbit back to a lower orbit. 4. The energy that is absorbed or emitted by an electron equals the energy difference between two orbits. According to the Bohr model, because electrons can exist only in certain orbits around the nucleus (not between these orbits), emissions from the hydrogen atom are seen only at particular wavelengths as a set of emission lines (a line spectrum) instead of as a continuous spectrum of all wavelengths. Likewise, in the absorption spectrum, the same wavelengths are exclusively absorbed (seen as black lines).
Explain why H2O is excluded from Keq expression ?
In this reaction, the concentration of water is omitted from the Keq expression because, although water is a reactant, it is also the solvent. As the solvent, the number of water molecules is significantly greater than the number of all other species in the solution; the HC2H3O2 is dilute and dissociates only to a small extent. Therefore, in relative terms, the [H2O] (55.5 M) is essentially constant and is omitted.
Infrared Spectroscopy
Infrared (IR) spectroscopy is a technique used to identify functional groups in a compound by analyzing the types of bonds present. The sample is irradiated with infrared light, which interacts with the bonds in the molecule. The amount of light absorbed is recorded by the detector, and the data collected is displayed on the IR spectrum as percent transmittance (y-axis) vs. wavenumber (x-axis). Transmittance is inversely related to absorbance (ie, if all the light is absorbed, there is 0% transmittance). The wavenumber (with units of cm−1) is the infrared frequency and is defined as the inverse of the wavelength. Because the wavenumber is related to wavelength, it is also directly related to frequency by the equation: - f=c/λ Therefore, IR spectroscopy measures absorbance at different frequencies. Frequency is directly related to energy. The energy needed to stretch a bond at a certain wavelength can be calculated using: - E=hf=hc/λ where E is energy and h is Planck constant. IR radiation ranges from 700 nm to 1 mm, and causes bond stretching vibrations and rotations at different frequencies. Functional groups absorb different amounts of energy depending on the type of bond present. Therefore, the intensity of the signals from bond-stretching vibrations and rotations at a certain frequency depends on the amount of energy absorbed. Spin-spin splitting of atoms is a phenomenon that occurs in nuclear magnetic resonance (NMR) spectroscopy. It revolves around how protons act in a magnetic field and the effect they have on the signals of neighboring protons.
In coordination chemistry, metal ions such as Gd3+ can act as ____ because they have empty valence orbitals that can readily accept electrons.
Lewis acids
Molar solubility shortcut for finding Ksp
MX: Ksp = x^2 MX2: Ksp = 4x^3 MX3: Ksp = 27x^4
How many electrons and neutrons are in Selenium-80 (Se-2) ?
Mass# - #protons = neutrons present 80 - 34 = 46 neutrons ions + #electrons = electrons present 2 + 34 = 36 electrons
spin-spin splitting
N+1 Rule: each proton senses # of equiv protons on adjacent atom splitting resonance peak into n+1
Arrhenius equation
The Arrhenius equation describes the relationship between the rate constant and the temperature and activation energy of a reaction. Both the rate constant and the rate of reaction decay exponentially with increasing activation energy and increase exponentially with increasing temperature. Because catalysts lower the activation energy of a reaction, the rate constant is greater for a catalyzed reaction than for an uncatalyzed reaction. Decreasing the activation energy Ea also gives a smaller exponential term, and therefore k increases exponentially with decreasing Ea. Conversely, k decreases exponentially with increasing Ea. According to the rate law equation, the rate of a given reaction is directly proportional to the rate constant. Therefore, the reaction rate also decreases exponentially with increasing Ea
The Heisenberg uncertainty principle states that
The Heisenberg uncertainty principle states that the position and momentum of a particle cannot both be precisely known at the same time. The uncertainty of the position and the uncertainty momentum are inversely proportional.
Which will remain in the flask in steam distillation -> 2-nitrophenol or 4-nitrophenol
The difference in connectivity of the constitutional isomers 2-nitrophenol and 4-nitrophenol causes the molecules to experience different intermolecular forces, which contributes to the difference in their boiling points. Because the hydroxyl and nitro groups in 2-nitrophenol are ortho and therefore close in proximity to each other, the hydrogen from the hydroxyl group can hydrogen bond intramolecularly with the lone pair of electrons on the nitro group. This intramolecular bonding decreases the number of intermolecular bonds that can form, thereby decreasing the boiling point of the compound. Because the hydroxyl and nitro groups on 4-nitrophenol are para, they are able to hydrogen bond intermolecularly but not intramolecularly. Intermolecular bonds hold the molecules of 4-nitrophenol together, thereby increasing the boiling point and causing it to stay in the flask while 2-nitrophenol distills. PICTURE: Left = 2-nitrophenol Right= 4-nitrophenol
law of mass action
The law of mass action states that the rate of a reaction is proportional to the molar amount of each reaction component raised to the power of its reaction order. For elementary reactions, the reaction order of each species is equal to its stoichiometric coefficient.
NMR shifts
The location of signals in the 1H NMR spectrum is known as the chemical shift, measured in ppm. The chemical shift depends on the electronic environment around protons. Protons with an electron cloud surrounding them are shielded from the magnetic field and exhibit an upfield signal, whereas protons adjacent to electronegative substituents are deshielded from the magnetic field and have a downfield signal. so if we add ester to a compound where the Hydrogen(s) is located, this will cause Hydrogen(s) to move downfield because ester deshields the hydrogen(s) so H will move from 3.8 to 4.36ppm
coordination number
The number of coordinate bonds attached to the central metal ion
Which of the following statements explains why the change in temperature of the H2O2 decomposition reaction using Fe(NO3)3 is approximately the same value as the change in temperature using NaI?
They do not affect the heat of the reaction (ΔH) "they don't affect thermodynamics"
Thin Layer Chromatography (TLC)
Thin layer chromatography (TLC) is a technique used to separate compounds based on polarity. The mobile phase (organic solvent) travels up the stationary phase, a thin absorbent plate coated with silica (SiO2), via capillary action. The components of a mixture travel up the plate at different rates based on their polarity. In normal phase TLC, nonpolar compounds have less affinity for the polar stationary phase than polar compounds, and therefore travel farther up the plate. PICTURE The only difference between the two compounds is the change from amine in 4-aminophenol to amide in acetaminophen. An amide is a hydrogen bond donor and acceptor via two electronegative atoms (oxygen and nitrogen) whereas an amine (primary and secondary) is a hydrogen bond donor and acceptor via only one electronegative atom (nitrogen). Because an amide has more hydrogen bond acceptors, it is more polar; therefore, spot B must be acetaminophen.
Tollen's Test
Tollens test is used to identify the presence of aldehydes and hydroxy ketones, including reducing sugars, which have a free anomeric carbon. It utilizes the oxidizing agent Ag(NH3)2+ to oxidize aldehydes to carboxylic acids. A positive Tollens test results in the formation of metallic silver that looks like a silver mirror deposited on the glassware. Ketoses such as fructose are hydroxy ketones. Ketones cannot be directly oxidized to carboxylic acids; however, hydroxy ketones can undergo tautomerization via an enediol intermediate to produce an aldehyde under Tollens test basic conditions. Because of this tautomerization, ketoses give a positive result to Tollens test.
Electrolytic cell
Using a loosely applied analogy, an electrolytic cell can be conceptualized as a galvanic (voltaic) cell that is operating in reverse. Although the electrolytic cells may be constructed differently (one chamber vs. two) and some chemical reactions are irreversible, accounting for these distinctions and limitations, electrolytic and galvanic cells essentially perform in an opposite manner. In a galvanic cell, a spontaneous, exergonic chemical reaction (ΔG < 0) produces electric current. Conversely, in an electrolytic cell, electric current from an external source (such as a battery) is supplied to drive a nonspontaneous, endergonic chemical reaction (ΔG > 0) within the electrochemical cell. In both galvanic and electrolytic cells, reduction takes place at the cathode and oxidation takes place at the anode, but the role of a given electrode is opposite in each cell type. The electrode functioning as the anode in a galvanic cell functions as the cathode in an electrolytic cell (and vice versa). As such, the direction of electrical current is reversed in an electrolytic cell compared with a galvanic cell. (Recall that, by convention, the direction of the electric current is taken to be opposite to the direction of electron migration.)
Charles' Law
V1/T1=V2/T2 (directly proportional) the law that states that for a fixed amount of gas at a constant pressure, the volume of the gas increases as the temperature of the gas increases and the volume of the gas decreases as the temperature of the gas decreases
Avogadro's Law
V1/n1=V2/n2 (directly proportional) as the vol increase, the # of moles increases
sp hybridization
a type of bonding where the 2s orbital mixes with only one of the three p-orbitals resulting in two sp orbitals and two remaining unchanged p orbitals
hydroxyls are poor LG, and are not readily eliminated during substitution rxn. What would make an alcohol a better leaving group ?
addition of an acid. -makes alcohol a good LG ! The addition of acid to an alcohol causes the hydroxyl group to become protonated, forming bound water with a positive charge on oxygen. Water is a weak base, and becomes neutral once it leaves. Therefore, protonation of an alcohol forms a good leaving group.
When ΔS° is positive and ΔH° is negative, the process is _______.
always spontaneous (−ΔG°).
d2sp3 hybridization
an octahedral set of six hybrid orbitals in which two d orbitals, one s orbital, and three p orbitals are combined
Types of Magnetism
diamagnetism, paramagnetism, ferromagnetism
what functional group forms in acid-cat. rxn bet. secondary amine and ketone/aldehyde ?
enamine
Consider the titration curve for aqueous ammonia shown below. (FLIP THE CARD TO SEE THE GRAPH) The quantity of hydrochloric acid required to reach the equivalence point in the titration is: A.9 mmol. B.10 mmol. C.12 mmol. D.16 mmol.
equivalence point is a point where acid or base is fully neutralized, where the number of equivalents of acid exactly equals the number of equivalents of base. If u look that point is at ~pH = 5.3 so if u trace it to the line and down we see that at this pH it is 100mL In this titration, 100 mL of 0.1 M HCl were required to reach the equivalence point. Accordingly, the number of millimoles of HCl required to reach this point is 100 mL × 0.1 mmol HCl/mL = 10 mmol HCl
ion product
helps us see where is the system in relation to equilibrium IP = [A^n+]^m[B^m-]^n we use the current concentrations of the ions (instead of equilibrium point concentrations like in Ksp) -gives a snapshot picture of what this solution looks like. -IP is analogous to rxn quotient (Q) (1) When solvent is unsaturated: IP<Ksp (solute will continue to dissolve) (2) when solution reaches equilibrium: IP = Ksp (saturated solution) (3) supersaturated: IP > Kspprecipitation occurs (and IP drops back down to Ksp)
Rault's Law is only valid for ___ mixtures. What happens when it is not ?
ideal the addition of a solute lowers the freezing point of a liquid according to the amount of solute added. As solute is added, the solvent's concentration decreases, leading to fewer solvent-solvent intermolecular interactions. However, the freezing point (a physical property) is not affected by the reactivity (a chemical property) of the solute. Properties that are affected by the amount but not the identity of the solute are called colligative properties.
what functional group forms in acid-cat. rxn bet. primary amine and ketone/aldehyde ?
imine
steam distillation
is a purification technique used to separate molecules based on boiling point. A liquid mixture is heated to a temperature that overcomes the intermolecular forces keeping the compound in the liquid phase. The vapors then condense in the collection flask as a liquid. A molecule that participates in strong intermolecular forces will have a higher boiling point than molecules with weak intermolecular forces. Hydrogen bonding can be intermolecular (between two molecules) or intramolecular (within the same molecule), and therefore can have a significant impact on a molecule's boiling point.
which has smaller dissociation energy ? pi bond or sigma bond
pi bond "double bond" = pi bond and sigma bond Pi bonds are created by the sideways overlap of p orbitals along a plane perpendicular to (ie, above and below) the internuclear axis. Because the overlap in electron density is not as efficient as for sigma bonds, pi bonds exist in a higher energy state and are not as stable as sigma bonds. As a result, they require less energy to be broken than sigma bonds
Heterocycles
ring structures that contain at least two different elements in the ring
name or point on periodic table 7 diatomic elements
row by noble gases look like "7" and hydrogen F,O,N, Cl,Br,I, and H ex. O2 or N2
sp2 hybridization
s, p, p orbital and 3 hybrid orbitals, trigonal-planar (120)
Fractional distillation
separation of a liquid mixture into fractions differing in boiling point (and hence chemical composition) by means of distillation, typically using a fractionating column.
Rault's Law
solvent mol fraction and its partial pressure at a given temperature are proportional. P total= PX + PX Raoult law states that the addition of any solute to a pure liquid lowers the freezing point and vapor pressure of the resulting solution. Solutes lower Temperature and Pressure.
When both ΔS° and ΔH° are positive, the process is _______.
spontaneous (−ΔG°) at high temperatures and nonspontaneous (+ΔG°) at low temperatures (ie, an endothermic reaction).
When both ΔS° and ΔH° are negative, the process is _______.
spontaneous (−ΔG°) at low temperatures and nonspontaneous (+ΔG°) at high temperatures (ie, an exothermic reaction).
Hund's rule states that
the order of orbital filling should maximize the number of unpaired electrons. Ferromagnetic and paramagnetic atoms and molecules have one or more unpaired electrons, which can align with a magnetic field. Therefore, they are attracted to magnets, and paramagnetic materials make good MRI contrast agents by enhancing the signal in tissues in which they have accumulated. In diamagnetic atoms and molecules, on the other hand, all electrons are spin-paired (all orbitals contain two electrons). Diamagnetic materials weakly repel magnets, and their magnetic moments align antiparallel to an applied magnetic field. Noble gases such as neon are diamagnetic, as are ions that have lost their outer shell unpaired electrons.
The change in Gibbs free energy ΔG° for a reaction at a given temperature is related to the equilibrium constant Keq by _______.
the relationship ΔG° = −RT ln Keq. The values of pH and ΔG° are related by the acid dissociation constant Ka, a special type of equilibrium constant. For instance if both Keq and T increases over the course of the experiment that means that ΔG° will decrease.. decrease.. decrease.. So now if you have a value to compare to you would say that increase in both Keq and T is less than the value that is given to you. Ex. ΔG° @ pH= 2.0 < ΔG° @ pH 2.6 (because Keq & T increase at pH 2)
Henry's Law
the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of the liquid solubility of gas increases as partial pressure of that gas increases
dsp3 hybridization
trigonal bipyramidal ex. SF4- 1 d-orbital, 1 s orbital, 3 p orbitals
