|E2 on sp2||
molecular mass = 57
|1 -OH------?-------> aldehyde||
- variable intensity
mechanism that is stereospecific: inversion of stereochemistry
triple bond in a molecule
Acetylene is a hydrocarbon belonging to the group of alkynes, considered to be the simplest of all alkynes as it consists of two hydrogen atoms and two carbon atoms.
mechanism where the reaction rate depends on the strength of the incoming base and the leavability of the leaving group
|tertiary amine---?----> quartenary amine||
alkyl halide/ NaOHC
decreases boiling point, melting point and density.
H2CrO4 (Aldehydes), Ag2O, O2 (Aldehydes, radical chain reaction), Powerful oxidants at high T and high acid or base concentration (e.g. HNO3) (Ketones)
1. DCC (dicyclohexyl carbodiimide) converts the OH of the carboxylate grp in an AA into a good leaving grp
2. amino grp of a 2nd AA attacks the carbonyl carbon of the "activated" AA
3. DCC leaves w/the oxygen to which it is bonded
Nitroso refers to a functional group in organic chemistry which has the general formula RNO.
|The higher the concentration||
The faster the rate
|Oxymercuration-Reduction: hydration #3||
-Hydration without using acid
- Markovnikov addition, BUT...
- No possibility of carbocation rearrangement
- Downside: toxic reagent
- Dont worry about the mechanism
Addition of O or removal of Hs
|Anhydride Reaction with H2O||
Makes two component acids
Carboxylic Acid + Alcohol -(H2SO4)-> Ester + H2O (Equilibrium Reaction)
a single polypeptide chain that is part of a large complex containing many subunits (a multisubunit complex)
A carbonate ester is a functional group in organic chemistry consisting of a carbonyl group flanked by two alkoxy groups.
|Boiling points depends on ____,____,____||
IMFS; Comparative BP's (alkans<ethers<amins<alcohols)
Halogens add to pi bonds because halogens are polarizable:
- C=C induces a dipole in X2: X+ - X -
- X is then attracted to the nucleophilic double bond
Proof that halogenation follows a different mechanism from that of hyrohalogenation or hydration:
- no carbocation rearrangements occur
- only anti addition of X2 is observed
- These facts suggest that carbocations are not intermediates.
|E2 if halide on 3||
Yes and Beta H
|Aromatic Transition States||
Found in: Decarboxylation of beta-keto acids and beta-dicarboxylic acids; Diels-Alder; Claisen Rearrangement; Cope Rearrangement
Polymerization of a monomer with at least two epoxygroups
- more deshielded (L)
Ex. a set of protons near an electroneg.grp is said to be deshielded & will appear downfield (L)
Postulated E levels of e were quantizedwhen an atom gives off an electron it moves into a higher level
atom or group of atoms which is electron withdrawing and has a tendency to be easily removed from a carbon structure
|Alcohols - Structure and Bonding||
-contain a hydroxy group (OH) bonded to an sp3 hybridized carbon
-classified according to the number of alkyl groups attached to carbon bearing the OH:
RCH2OH = 1
R2CHOH = 2
R3COH = 3
|Alkene-----?------ adds -OH and H marks rule||
1. Hg(OAc)2/ 2. NaBH4
|Alcohols (Mass Spec)||
Commonly lose H2O, giving strong M-18 peak (and almost no M peak); can also lose an alkyl group from R-CR'2-OH to give R-radical and resonance stabilized CR'2=OH+
|common oxidizing agents (able to absorb e⁻ & be reduced)||
Chromic Acid (H₂CrO₄)
Chromate Salts (CrO₄²⁻)
Dichromate Salts (Cr₂O₇²⁻)
Chromium Trioxide (CrO₃)
Pyridinium Chlorochromate (PCC)
E1 is a model to explain a particular type of chemical elimination reaction in which there is a two-step process of elimination ionization and deprotonation.
|Effect of Leaving Group||
A better leaving group increases the rate of both Sn1 and Sn2 reactions
|Preparation of Alkenes: Refresher||
Alkenes can be prepared from alkyl halides, tosylates, and alcohols via elimination reactions.
The most stable alkene is usually formed as the major product.
|Chain Transfer Reaction||
Radical changes places with H to give more stable radical, which results in branching
|Sn2 rate speed R||
The more r groups, the slower the reaction
|Comparing E1 & E2 Reactions: Stereoselectivity||
-if C from which H is removed is bonded to 2 H, get mostly E some Z
-if C from which H is removed is bonded to 1 H, get mostly anti elimination (can be mostly E or mostly Z)
-Get mostly E
|Mechanism of Ether Cleavage||
The mechanism of ether cleavage is Sn1 or Sn2, depending on the identity of R.
When 2 or 3 alkyl groups are bonded to the ether oxygen, the C-O bond is cleaved by an Sn1 mechanism involving a carbocation.
With methyl or 1 R groups, the C-O bond is cleaved by an Sn2 mechanism.
|Carboxylic Acid Derivative Reaction with Gilman||
Acid Chloride (and no others) ---(1. R2CuLi, Ether, 78oC, 2. H2O)---> Ketone
|Racemization in Sn1 reactions||
Step 1: loss of the leaving group in generates a planar carbocation (achiral)
Step 2: Attack by :Nu can occur on either side to afford two products, which are a pair of enantiomers.
Because there is no preference for nucleophilic attack from either direction, an equal amount of the two enantiomers is formed - a racemic mixture (process is called racemization)
hydrogenation of π bonds of alkynes
- H₂ (w/2 equivalents)
- complete reduction
- uses Ni, Pd, or Pt
|Syn and Anti Addition to Alkenes||
Because the carbon atoms of a double bond are both trigonal planar, the elements of X and Y can be added to them from the same side or from opposite sides:
- syn addition: both X and Y are added from the same side
- anti addition: X and Y are added from opposite sides
|Comparison of E1 and E2 Mechanisms||
The strength of the base is the most important factor in determining the mechanism for elimination.
-much more common and useful
-favored by strong, negatively charged bases, especially -OH and -OR
-The reaction occurs with 1, 2, and 3 alkyl halides.
-much less useful because a mixture of Sn1 and E1 products usually results
-favored by weaker, neutral bases, such as h2o and ROH
|High temperature range||
molecular mass = 29
|2 -OH----?------> Ketones||
- broad, strong
|E1 if halide on 1||
5-membered: -pyran- 6-membered: -furan-
In chemistry racemization refers to partial conversion of one enantiomer into another, which often occurs in SN1 substitution.
polar protic solvents (SN1 or SN2)
|secondary amine---?----> tertiary amine||
allkyl halide/ NaOH
Technique used to separate two miscible liquids
Identical configurations at each stereocenter
- always look for this 1st
- very strong & very intense
An electrophilic addition reaction is an addition reaction where, in a chemical compound, a pi bond is removed by the creation of two new covalent bonds.
Ozonolysis is the cleavage of an alkene or alkyne with ozone to form compounds in which the multiple carbon-carbon bond has been replaced by a double bond to oxygen.
|Polar aprotic solvents||
No OH or NH bonds
|Degree of Unsaturation||
Unsaturated hydrocarbons: have fewer than the maximum number of hydrogen atoms per carbon (2n+2) (alkenes, alkynes)
Each pi bond or ring removes two hydrogen atoms from a molecule, and this introduces one degree of unsaturation.
Degree of unsaturation: the number of pi bonds and cyclic strctures in a molecule (remember: a oduble bond has on pi bond, a triple bond has two pi bonds)
General formula for hydrocarbon: CnH2n+2-2x where x is the degree of unsaturation in the molecule
Occurs when a crystallizing mixture is cooled too quickly
Amide --(1. LiAlH4, 2. H2O)--> Amine
Thermal rearrangement of allyl phenyl ethers to 2-allylphenols (oxygen is a member of the rearrangement ring)
- relatively strong WEAK acids
- c.acids form strong hydrogen bonds bc the carboxylate grp contains both a H-bond donor & a H-bond acceptor
- c.acids that have carbonyl grps β to the carboxylate are unstable
A thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom. Often referred to as mercaptans, these compounds are the sulfur analogues of alcohols.
An electron goes into the atomic orbital with the lowest energy first
With an unsymmetrical alkene, HX can add to the double bond to give two constitutional isomers, but only one is actually formed.
- the electrophile (often H) adds to the sp2 carbon that is bonded to the greater number of hydrogens.
- in the addition of HX to an unsymmetrical alkene, the H atom adds to the less substituted carbon atom - that is, the carbon that has the greater number of H atoms to begin with
- "them that has, gets"
- results in formation of the most stable carbocation.
|E2 if halide on 2||
Yes and beta H
|Cyclic Structure of Monosaccharides||
Monosaccharides almost entirely exist as five and six membered hemiacetals
|ALL animal AA:||
are derived from L-glyceraldehyde, & are thus all L-configuration
Partial plus (< full +1 ion charge) or partial minus (< full -1 electron charge) dipole charge
One sigma bond breaks and another one forms
|Reactivity of Hydrogen Halides||
-The reactivity of hydrogen halides increases with increasing acidity.
-Cl- is so poor a nucleophile that an additional lewix acid catalyst (ZnCl2) is needed with 1 ROH.
-Complexation of ZnCl2 with the O of ROH makes a very good leaving group that facilitates the Sn2 reaction.
A violent surge which can occur when a liquid is heated without boiling stones
|Carboxylic Acids (Mass Spec)||
Alpha-cleavage to give COOH+ (m/z=45); Also, McLafferty Rearrangement
1. adds substituant to the most substituted C available
2. rearrangements possible
3. major/minor products
4. two steps
|Syn and Anti addition||
Syn and anti addition are different ways in which two substituents can be added to a double bond or triple bond.
|Predicting the Mechanism of Nucleophillic Substitution Reactions||
Four factors are relevant in predicting whether a given reaction is likely to proceed by an Sn1 or an Sn2 mechanism:
-The alkyl halide - CH3X, RCH2X, R2CHX, R3CX
-The nucleophillic - strong or weak
-The leaving group - good or poor
-The solvent - protic or aprotic
|Halogenation: Electrophilic Addition of Halogen||
Halogenation: addition of X2 (X=Cl or Br) to an alkene to form a vicinal dihalide.
|Reduction of COOH||
Only LiAlH4, which takes it to 1o alcohol
|Pka trend of good leaving groups||
Low pka values because strong conjugate acids
|Substitution and Elimination Reactions of Alcohols||
-Treatment of alcohols with a strong acid protonates the O converting the bad leaving group -OH into h2o, a good leaving group.
This makes it possible to perform substitution and elimination reactions on alcohols.
|1 -OH-----?------> carboxylic acid||
CrO3/ H3O, actone or KMnO4, OH/ H2O, heat
|Acid Chloride Reaction with H2O||
R-COCl + H2O --> R-COOH + HCl
|Substrate Reactivity in Sn1 reactions||
Sn1 reaction rate is affected by the type of alkyl halide involved: As the number of R groups on the carbon with the leaving group increases, the rate of an Sn1 reaction increases.
(Sn2 Factor = stereo factor) (Sn1 Factor = carbocation stability)
|unsaturated fatty acids||
- fatty acids have 1 or more doubB in the tail
- almost always Z (cis)
|In words, what Does adding POCl3/ pyridine to a 2 -OH do?||
It dehyrdates the alcohol and creates a double bond
|Reactions of Ethers with Strong Acid||
When ethers react with HBr or HI, both C-O bonds are cleaved and two alkyl halides are formed as products.
Ethers are unreactive with everything except HX, so ethers are commonly used as solvents:
-diethyl ether, tetrahydrofuran, tetrahydropyran, 1,4 dioxane, 1,2-dimethoxyethane, tert-butyl methyl ether
|Sn2 on sp2||
molecular mass = 15
|ether------?-----> alcohol + alkene||
2 monosaccharides bonded together
|Sn2 if halide on 1||
|Grignard Reagents with a,b-Unsaturated Carbonyl||
Traditionally known as acetylenes or the acetylene series, the alkynes are hydrocarbons that have at least one triple bond between two carbon atoms.
relative reactivity of solvents (water and ethanol for SN1 reactions)
|primany amine----?-----> secondary amine||
alkyl halide/ NaOH
Condition where liquid collects on glassware and reduces the amount of liquid distilled
|1,2 vs. 1,4||
1,2 Kinetic 1,4 Thermodynamic
- look for this 2nd
- variable intensity
An aldehyde is an organic compound containing a terminal carbonyl group.
Employing borane in tetrahydrofuran in the first step, the hydroboration-oxidation reaction is a two-step organic chemical reaction that converts an alkene into a neutral alcohol by the net addition of water across the double bond.
|Conjugate base is stuff (with or without) added proton||
Suspension of one material in another that does not separate quickly by gravity
Ketone or Aldehyde loses an alpha-hydrogen (to a base), giving a resonance stabilized anion
Aldehydes and ketones with an alpha-H can react over acid or base with X2 to give alpha-Halo-...one
180°Two atoms bound to central atom, no lone pair
Acetyl (ethanoyl), is the term for a functional group which is the acyl of acetic acid.
An alcohol is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom of an alkyl or substituted alkyl group
when an electron in a sigma orbital can overlap with an anti-bonding orbital
Alkyne nomenclature similar to that of alkenes.
In the IUPAC system, change the -ane ending of the parent alkane name to the suffix -yne.
Choose the longest continuous chain that contains both atoms of the triple bond and number the chain to give the triple bond the lower number.
Diyne: compound containing two triple bonds
Triyne: compound contatining three triple bonds
Enyne: compound containing both a double and triple bond
-number chain to give first unsaturation (C=C or CtripleC) the lower number
less stable, more energy and more polar
A polymer that can be melted and molded into a shape which it will retain when cooled
- chemical assay that detects the carbonyl units of sugars
- distinguishes hemiacetals from acetals
- Benedict's reagent is used to oxidize a sugar's aldehyde ketone to the corresponding carboxylic acid, yielding a reddish precipitate
N=2 and l=0Middle looks like 1s with a node and then a raise and fall in density
|E on diagram||
Determines the height of the energy barrier
|Stereochemistry of Reaction of Alcohols with HX||
As in other substitution reactions,
-Sn2 reactions give inverted
-Sn1 reactions give raceimization
How far a compound travels on TLC relative to the solvent
A diene reacts with a dienophile (most double or triple bonds) to give a cyclic compound (bicyclic if the diene is already cyclic) Electron Releasing Groups activate dienes, EWGs activate dienophiles
- compounds that have the same mol. formula & same connectivity. They differ in respect of rotation around a single bond
- staggered vs. eclipsed
A nitrite is either a salt or an ester of nitrous acid.
|Stereochemistry of Sn1 reaction||
Nucleophile attacks either side of the carbocation.
|Epoxide Reaction with Nucleophiles: Regioselectivity||
Nucleophile opens epoxide ring from the back.
Regioselective: in unsymmetrical epoxides, the nucleophile attacks the less substituted C.
|free-radical halogenation (4 steps)||
1. initiation: can be initiated by light or heat
2. propagation: no net change in the # of radicals
3. termination: net decrease in the # of radicals. rxn continues until one of the reactive radicals of the propagation steps combines w/another radical
4. inhibition: rxn is inhibited by molecular oxygen. can happen ANYTIME, not necessarily after termination
|The larger the energy of activation rate constant||
The smaller the rate constant
|Mechanism of Reaction of Alcohols with HX||
More substituted alcohols usually react more rapidly with HX
The mechanism depends on the structure of the R group.
|ester-----?-------1 -OH + 3 -OH||
Gringard with 1. R-Mg-X, ehter/ 2. H3O
|Nitrile Reaction with H2O||
R-Cl + KCN --> R-CN -(H2SO4, H2O, Heat)-> R-COOH or R-CHO + HCN, KCN --> R-OH-CN -(H2SO4, H2O, Heat)-> R-COOH (Can stop at amide if controlled)
|E2 Dehydration of 1 Alchols I||
1 carbocations are highly unstable -> 1ROH do not undergo E1
1ROH undero dehydration by way of an E2 mech.
|Valence Shell Electron Pair Repulsion Theory (VSEPR theory)||
In covalent molecules both bonded and lone pairs of e- repel eachotherMolecules assume shape to keep all e- as far away frome each other as possibleSolid straight line is on planeSolid Wedge towards readerdash wedge away from reader
|3 OH--------?------> most sub alkene is major + H2O||
Dehydration H3O, THF This is an E1 mechanism
|2 OH or 1 OH ------?------- Alkene (+OPOCl2)||
POCl3/ pyridine this is an E2 mechanism
|Reactive intermediate name||
polar, neutral AAs
|Sn1 number of steps||
|E1 on benzylic C||
bond angles (ideal)
|Solvent preference sn1||
Polar protic solvents
|Good nuc effect on Sn2||
- synonym for hydrophobic
Ethylene is a chemical compound containing two carbons and four hydrogens. It is the simplest alkene.
|A larger atom is (more/less) stable||
1. LiAlH4, ether/ 2. H2O
Reaction of an organometallic compound with a ketone to an alcohol
Random configurations at each stereocenter
Two waves in different phase
The term sulfide refers to several types of chemical compounds containing sulfur in its lowest oxidation number of -2.
SN2 reaction with water as the nucleophile (slowest or fastest)
|sp3 carbons are called "________ Carbons"||
|Tertiarty -OH ------?---------> tertiary alkyl halide||
(Sn1) HCl or HBr
|What is a completely useless reaction for synthesis?||
|Acetoacetic Ester (AAE)||
CH3-CO-CH2-CO-OEt can make substituted acetone by making enolate of AAE, alkylating, then saponification, acidification, and decarboxylation.
- separation by density
- for large macromolecules
120°Three atoms bound to central atom with no lone pair
Gilman reagents are lithium and copper reagent compounds which are useful because they react with chlorides, bromides, and iodides to replace the halide group with an alkyl group.
Elements in the starting material are lost and a bond is formed
|Summary of Sn2||
Kinetics - Second-order kinetics; rate = k[ RX][Nu-]
Mechanism - one step
Stereochemistry - Backside attack of the nucleophile, inverison of configuration at a stereogenic center.
Identity of R - Unhindered halides react fastest
Process by which the mobile phase moves up the stationary phase
Hydrolysis of an Ester in aqueous base (consumes 1 mole base)
- species that have unshared pairs of electrons or π bonds &, frequently, a neg charge
- electron pair donors
|what affects BP||
1. intermolecular forces
2. mass ∝ BP
3. branching ∝ BP⁻¹
A disulfide bond is a single covalent bond derived from the coupling of thiol groups.
|Delta h on diagram||
Determines the relative position of the reactants and products
|Reactions of Epoxides||
Epoxides do not contain a good leaaving group.
Epoxides do contain a strained three-membered ring with two polar bonds.
Epoxides can react with HX or with nucleophiles.
|Amines (Mass Spec)||
Beta-cleavage of 1o, 2o, and 3o aliphatic
|column (flash) chromatography||
- separates by polarity
- like TLC upside down & thru sand
A solvent that has a hydrogen atom bound to an oxygen as in a hydroxyl group or a nitrogen as in an amine group.
|The higher the energy species stability||
The less stable the species
When an alchol has two or three beta carbons, dehydration is regioselective and follows Zaitsev's rule.
The more substituted alkene is the major product when a mixture of constitutional isomers is possible.
|Ketone -----?------> 3 -OH||
Gringard with 1. R-Mg-X, ether/ 2. H3O
- the more stable the anion, the less basic it is
- resonance stabilization or powerful e⁻ withdrawing grps will decrease basicity
|If pKa is greater than the pH it is an (acid/base)||
|Cis/Trans Differ in Physical Properties||
Consequence of alkene polarity:
- cis and trans isomeric alkenes have different physical properties
- cis-2-butene b.p.: 4 C (net dipole) higher bp
- trans-2-butene b.p.: 1 C (no net dipole) lower bp
|Molecular Ion Fragmentation||
Gives a Cation and a Radical (only the cation is detected by the mass spec) (cation stability more important than radical stability)
|peptide bonds vs. disulfide bridge||
peptide bonds link AAs together into polypeptide chains
disulfide bridges link b/w cysteine R-groups
|Regioselectivity of Epoxide Ring Opening||
Ring opening of an epoxide with either Nu or HZ is regioselective becasue one constitutional isomer is the major or exclusive product.
The site selectivity of these two reactions is exactly opposite.
|What mnemonic is used to calculate the strength of a base?||
Charge - more neg, stronger base
Atom - Smaller the atom, stronger the base
Resonance - Least resonance, stronger the base
Dipole Induced - The further the EN atom is from the O, the stronger the base
O - Further the lone pair from the nucleus, stronger the base
|Additon of Nitrogen Nucleophiles (Primary) to Carbonyls||
Ammonia or 1o amines react with C=O to give imines (loss of H2O)
|Oxidation of an alcohol yields what? If the resulting species is oxidized again, what is formed?||
Oxidation is when we increase the # of bonds between C and O
Alcohol --> Aldehyde --> Carbox Acid