Term
| some excellent nucleophiles |
|
Definition
| -N3-
-NC-
-HS-
-RS-
-HO-
-RO-
-H-C≡C- |
|
|
Term
|
Definition
| -F-
-Cl-
-Br-
-I-
-RO2-
-R-SH
-R3N
-R2NH
-RNH2 |
|
|
Term
|
Definition
| -H2O
-R-OH
-RO2H
-(CH3)3CO- |
|
|
Term
| some reagents that are essentially non-nucleophilic |
|
Definition
|
|
Term
| characteristics of a good nucleophile |
|
Definition
| strong base and, when applicable, polarizeable |
|
|
Term
| when base strength and nucleophilicity parallel each other |
|
Definition
|
|
Term
| why HSO4- is essentially non-nucleophilic |
|
Definition
| because the negative charge is on O |
|
|
Term
|
Definition
| -HO-
-RO-
-H2N-
-H-
-R-
-R2N
-(CH3)3CO-
-H-C≡C- |
|
|
Term
| basicity vs. e'negativity |
|
Definition
|
|
Term
| polarizeability vs. base strength |
|
Definition
|
|
Term
| some excellent leaving groups |
|
Definition
| -I-
-Br-
-Cl-
-TsO-
-MsO-
-H2O |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| base strength vs. leaving group ability |
|
Definition
|
|
Term
| some polar protic solvents |
|
Definition
| -H2O
-CH3OH (MeOH)
-CH3CH2OH (EtOH)
-(CH3)3COH (t-BuOH)
-CH3COOH (AcOH) |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| some polar aprotic solvents |
|
Definition
| -DMSO
-CH3CN (acetonitrile)
-CH3COCH3 (acetone)
-DMF
-HMPA |
|
|
Term
|
Definition
| in general, they are solvents with O-H or N-H bonds |
|
|
Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
|
Definition
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Term
|
Definition
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Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
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|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| what happens in an SN1 rxn? |
|
Definition
| nucleophile attacking carbocation |
|
|
Term
| what happens in an E1 rxn? |
|
Definition
| deprotonation of the C adjacent to the carbocation |
|
|
Term
| the rate limiting step in SN1 rxns |
|
Definition
| formation of a carbocation |
|
|
Term
| the rate limiting step in E1 rxns |
|
Definition
| formation of a carbocation |
|
|
Term
| the rate of an SN1 rxn depends on... |
|
Definition
| only the concentration of the substrate |
|
|
Term
| the rate of an E1 rxn depends on... |
|
Definition
| only the concentration of the substrate |
|
|
Term
| the rate of an SN1 rxn is proportional to... |
|
Definition
| the stability of the carbocation |
|
|
Term
| the rate of an E1 rxn is proportional to... |
|
Definition
| the stability of the carbocation |
|
|
Term
| carbocations in order of stability |
|
Definition
| tertiary > secondary >> primary > methyl |
|
|
Term
| the solvents favored in rxns involving carbocations |
|
Definition
|
|
Term
| the shape of carbocations |
|
Definition
|
|
Term
| carbocations are stabilized by... |
|
Definition
-increasing substitution at C
-resonance |
|
|
Term
| carbocations can be formed by... |
|
Definition
-dissolving tertiary alkyl halide in a polar protic solvent
-adding acid to a secondary or tertiary alcohol |
|
|
Term
| carbocations are more stable in these solvents |
|
Definition
|
|
Term
| secondary carbocations can rearrange to tertiary carbocations by... |
|
Definition
|
|
Term
| some carbocations that are very unstable other than primary and methyl |
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| some ways to form carbocations |
|
Definition
-dissolve tertiary alkyl halides in polar protic solvent
-add an acid to a secondary or tertiary alcohol
-addition of silver salts to an alkyl halide |
|
|
Term
| some ways secondary carbocations can rearrange to tertiary carbocations |
|
Definition
-hydride shift
-alkyl shift
-ring expansion
the driving force is formation of more stable carbocation |
|
|
Term
|
Definition
1: departure of leaving group
2: nucleophile attacking the carbocation |
|
|
Term
| why SN1 rxns lead to racemization |
|
Definition
| because the carbocation is flat |
|
|
Term
| SN1 rxns are always accompanied by... |
|
Definition
|
|
Term
|
Definition
1: departure of leaving group
2: deprotonation of carbon adjacent to carbocation |
|
|
Term
| in E1 rxns, the proton is removed by... |
|
Definition
|
|
Term
| the 2bl bond that is favored in E1 rxns |
|
Definition
| the more substituted one (Zaitsev) |
|
|
Term
| stereochemistry of 2bl bond product of E1 rxns |
|
Definition
| the major product will have the bulkiest groups trans to each other across the 2bl bond |
|
|
Term
| E1 rxns are favored by... |
|
Definition
|
|
Term
| the base in E1 rxns can be... |
|
Definition
| the solvent, leaving group, the counter-ion of the acid |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| effect of 2bling the concentration of the substrate in SN1 rxns |
|
Definition
|
|
Term
| effect of 2bling the concentration of the nucleophile in SN1 rxns |
|
Definition
|
|
Term
| effect of 2bling the concentration of the substrate in E1 rxns |
|
Definition
|
|
Term
| effect of 2bling the concentration of the nucleophile in E1 rxns |
|
Definition
|
|
Term
| in 6-membered rings, E2 rxns can occur only when... |
|
Definition
| the leaving group is axial |
|
|
Term
| in 6-membered rings, SN2 rxns can occur only when... |
|
Definition
| the leaving group is axial |
|
|
Term
| why E2 rxns in 6-membered rings can occur only when the leaving group is axial |
|
Definition
| because there needs to be a H anti-periplanar to the leaving group |
|
|
Term
| why SN2 rxns in 6-membered rings can occur only when the leaving group is axial |
|
Definition
| because the antibonding orbital is accessible and above the ring only when the leaving group is axial |
|
|
Term
| rate of SN2 rxn vs. steric bulk |
|
Definition
|
|
Term
| the one thing mass spectroscopy is great for |
|
Definition
| determining the molecular mass of the unknown sample |
|
|
Term
| the most important peak to identify in mass spectroscopy |
|
Definition
|
|
Term
| significance of the "molecular ion" (M+) |
|
Definition
| it's the mass of the parent molecule minus an electron |
|
|
Term
| some other things that can be learned from mass spectroscopy |
|
Definition
-whether or not certain halogens (Br, Cl) are present
-the structure of the molecule |
|
|
Term
| how one can use mass spectroscopy to determine whether or not certain halogens (Br, Cl) are present |
|
Definition
| by analyzing the M+2 peaks |
|
|
Term
| how mass spectroscopy can help identify the structure of the molecule |
|
Definition
the fragmentation pattern provides clues about the structure of the molecule, since molecules break at their weakest points
the question "what is the most stable free radical that can be formed" is a good place to start |
|
|
Term
| the 3 types of info one can get from a mass spectrum |
|
Definition
-the molecular ion M
-fragment masses (M-X "M minus X")
-isotope masses; they give info about # of C's (M+1), presence of halogens (M+2), or other atoms (like S and Si) |
|
|
Term
| the parent ion in mass spectroscopy |
|
Definition
| the highest intensity peak (assigned intensity of 100), usually representing the most favorable fragmentation of the molecule |
|
|
Term
| some variation of the M peak in mass spectroscopy |
|
Definition
the strength of it varies considerably
strong for alcohols, but can be very weak for aldehydes |
|
|
Term
| the sequence of mass spectroscopy |
|
Definition
1: sample injection
2: ionization
3: acceleration
4: deflection (separation)
5: detection |
|
|
Term
| details about sample injection in mass spectroscopy |
|
Definition
| the sample (as a dilute solution) is injected into a receptor, and then "nebulized" into gaseous form |
|
|
Term
| details about ionization in mass spectroscopy |
|
Definition
| the sample is hit with a high energy electron beam, knocking an electron off of the molecule and forming a positive ion (molecular ion, M+) |
|
|
Term
| details about acceleration in mass spectroscopy |
|
Definition
the molecular ion M (and whatever fragments they may have broken into) are accelerated in an electric field
(neutral fragments can't be accelerated by the electric field and won't be detected) |
|
|
Term
| details about deflection (separation) in mass spectroscopy |
|
Definition
the stream of ions is deflected by a magnetic field located along a bend in the tube
this separates the ions according to their mass/charge ratio (M/Z), as lighter ions will be "bent" more than heavier ones |
|
|
Term
| details about detection in mass spectroscopy |
|
Definition
the ions hit a detector which converts the arrival of each ion into an electrical signal, which is amplified and recorded
the instrument can be "tuned" to optimize sampling of fragments with a particular range of masses |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| how to use the M+1 peak to determine the number of C's in mass spectroscopy |
|
Definition
| divide the M+1 peak by 1.1% |
|
|
Term
| how the M+2 peak can help you detect Cl or Br |
|
Definition
if the M+2 peak is about equal to M, 1 Br is present
if the M+2 peak is about 1/3 the height of M, 1 Cl is present |
|
|
Term
| one way to detect S on a mass spectroscopy reading |
|
Definition
| S also has a significant M+2 peak, although about 4% the intensity of M for each S present, it is much smaller |
|
|
Term
| what does it mean when M is odd? |
|
Definition
| the number of N's in the sample is odd |
|
|
Term
| what happens when a sample is hit with a high-energy electron beam? |
|
Definition
| it results in an unstable high-energy species (the molecular ion) which may fragment before detection |
|
|
Term
| when fragmentation occurs, it forms... |
|
Definition
-a cation (which is detected)
-a (neutral) free radical (which is not) |
|
|
Term
| an important clue to understanding which fragments will form in fragmentation |
|
Definition
| understanding "what are the most stable carbocations/radicals that can be formed thru breaking bonds in the molecule?" |
|
|
Term
| sequence of fragmentation in mass spectroscopy |
|
Definition
1: the molecule is hit by a high energy electron beam and an electron is ejected from the sample, creating a cation
2: the resulting cation is an unstable high energy species which has a very short lifetime and might fragment before detection
3:
3a: fragmentation may occur to give a neutral fragment (a radical) not detected and a cation fragment (which can be detected)
3b: many different fragmentations may occur, but ones that result in relatively stable fragments will be most likely |
|
|
Term
| how to analyze a mass spectroscopy chart |
|
Definition
1: look for the molecular ion M, usually the peak furthest right
2: look for the highest intensity fragments and try to figure out how they might have formed from the substance being analyzed |
|
|
Term
| something that helps predict fragmentation patterns |
|
Definition
| carbocation (and radical) stability |
|
|
Term
| stability of carbocations vs. stability of C radicals |
|
Definition
|
|
Term
| the bond breaking that is usually most likely to occur in mass spectrometry |
|
Definition
| the bond breaking that forms the most stable carbocations/radicals |
|
|
Term
| some things IR spectroscopy can be useful for |
|
Definition
-identifying certain functional groups
-most useful for determining the presence or absence of hydroxyl (OH) and carbonyl (C=O) groups
-more rarely, determining the presence or absence of amines or amides (N-H bonds) as well as terminal alkynes
-can be useful for determining the presence of alkenes/aromatics as well as CC and CN triple bonds |
|
|
Term
| the questions to ask when using IR spectroscopy |
|
Definition
-Is a hydroxyl group present?
-Is a carbonyl present?
-Are there any triple bonds?
-Is an amide or amine present? |
|
|
Term
| number of atoms vs. frequency |
|
Definition
|
|
Term
| size of bonded atoms vs. frequency |
|
Definition
|
|
Term
| electrions can be promoted to higher energy levels (i.e. orbitals) when... |
|
Definition
| a molecule absorbs UV or visible light of frequency ΔE, where ΔE is the difference between energy levels |
|
|
Term
| some ways molecules can vibrate |
|
Definition
-symmetric stretching
-asymmetric stretching
-bending
-scissoring
-rocking |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| the bottom line for IR spectroscopy |
|
Definition
| different bonds absorb IR radiation at characteristic frequencies and we can use these patterns to identify certain functional groups present in an unknown sample |
|
|
Term
| how IR spectroscopy is done |
|
Definition
| the sample, often a thin film, is exposed to a burst of infrared light, and the absorbance of the sample is measured vs. the frequency of the light |
|
|
Term
| how the IR spectrum is usually plotted |
|
Definition
| usually transmittance on the y axis vs. wave number on the x axis measured in cm-1, which correlates the frequency |
|
|
Term
|
Definition
the inverse of wavelength (1/λ)
λ = wavelength |
|
|
Term
| how wavelength is related to frequency |
|
Definition
λ = v/c
λ = wavelength
v = frequency
c = the speed of light |
|
|
Term
| wavenumber corresponds to... |
|
Definition
| the number of wavelengths per unit distance |
|
|
Term
| the 4 key principles to apply in order to determine whether C atoms are "chemically shift equivalent" |
|
Definition
1: equivalence thru rotation of the whole molecule
2: equivalence thru symmetry (mirror planes)
3: equivalence thru fast rotation
4: inequivalence due to stereochemistry |
|
|
Term
| equivalence thru rotation of the whole molecule |
|
Definition
| when atoms are chemically equivalent if their positions can be superimposed by rotation of the molecule |
|
|
Term
| equivalence thru symmetry (mirror planes) |
|
Definition
| when C atoms are equivalent if they can be interconverted by reflection along a mirror plane |
|
|
Term
| equivalence thru fast rotation |
|
Definition
| C's being chemically shift equivalent when they can be interconverted thru bond rotations |
|
|
Term
| the 4 key principles to apply in order to determine whether H atoms are "chemically shift equivalent" |
|
Definition
1: equivalence thru fast rotation
2: chemical equivalence thru reflection in a mirror plane
3: chemical equivalence thru rotation of the whole molecule
4: homotopic, enantiotopic, and diastereotopic H's |
|
|
Term
|
Definition
| chemically equivalent and will have the same chemical shifts |
|
|
Term
|
Definition
| chemically equivalent in an achiral environment |
|
|
Term
|
Definition
| chemically inequivalent and will therefore have different chemical shifts |
|
|
Term
|
Definition
| because it has a nuclear spin of 0 |
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
| speed of light (≈ 3 • 108 m/s) |
|
|
Term
|
Definition
| energy (J / mol or kJ / mol) |
|
|
Term
| how to calculate wavelength (λ) |
|
Definition
|
|
Term
| how to calculate frequency (v) |
|
Definition
|
|
Term
| how to calculate energy (ε) |
|
Definition
|
|
Term
|
Definition
|
|
Term
| what undergoes McLafferty rearrangement? |
|
Definition
|
|
Term
| ketones do this to form alcohols and alkenes |
|
Definition
|
|
Term
| ketones undergo Mclafferty rearrangement to form... |
|
Definition
|
|
Term
| the most ubiquitous gfragment in the mass spectrum |
|
Definition
| the one that forms the most stable carbocation |
|
|
Term
| why H's at the end of a 2bl bond can count as 2 different kinds of H's |
|
Definition
| because 1 is cis and the other is trans |
|
|
Term
| convert chemical shift into δ units (δ = ppm) |
|
Definition
δ = (observed chemical shift (Hx away from TMS)) / (spectrometer frequency in MHz)
δ = ppm |
|
|
Term
| relationship between measurements in δ units (ppm) and frequency of spectrometer |
|
Definition
| δ measurements in ppm are totally independent of spectrometer frequency |
|
|
Term
|
Definition
the left part of the NMR chart
aka low-field |
|
|
Term
|
Definition
the right part of the NMR chart
aka high-field |
|
|
Term
|
Definition
| the position on an NMR chart at which a nucleus absorbs |
|
|
Term
| What's the chemical shift? R-OH and R-NH2 |
|
Definition
|
|
Term
| What type of H? 0.5-8 δ (ppm) |
|
Definition
|
|
Term
| What's the chemical shift? [image] |
|
Definition
|
|
Term
| What type of H? 10-? δ (ppm) |
|
Definition
|
|
Term
| What's the chemical shift? [image] |
|
Definition
|
|
Term
| What type of H? 9.3-9.7 δ (ppm) |
|
Definition
|
|
Term
| What's the chemical shift? [image] |
|
Definition
|
|
Term
| What type of H? 6.6-8.1 δ (ppm) |
|
Definition
|
|
Term
| What's the chemical shift? [image] |
|
Definition
|
|
Term
| What type of H? 5-6.4 δ (ppm) |
|
Definition
|
|
Term
| What's the chemical shift? [image] |
|
Definition
|
|
Term
| What type of H? 2.8-3.7 δ (ppm) |
|
Definition
|
|
Term
| What's the chemical shift? [image] |
|
Definition
|
|
Term
| What type of H? 1.8-2.7 δ (ppm) |
|
Definition
|
|
Term
| What's the chemical shift? R3C-H, R-CH2-R, and R-CH3 |
|
Definition
|
|
Term
| What type of H? 0.7-1.8 δ (ppm) |
|
Definition
|
|
Term
| What's the chemical shift? Si(CH3)4 |
|
Definition
|
|
Term
| What type of H? 0 δ (ppm) |
|
Definition
|
|
