question

Leaving group:

answer

halide sometimes or any other electronegative group. This is the group that is displaced in a substitution of lost in elimination.

question

Electrophile:

answer

electron loving, Lewis Acid

question

Nucleophilic substitution:

answer

Any reaction in which one nucleophile (nucleus loving) is substituted for another at the tetravalent carbon atom, Lewis base

question

β-Elimination:

answer

A reaction in which a molecule such as HCl, HBr, HI, or HOH id split out or eliminated from adjacent carbons

question

POINTS FOR NUCLEOPHILIC SUBSTITUTION

answer

1.) If the nucleophile is negatively charged, the atom donating the electrons will become neutral
2.) If the atom is neutral, then the atom donating the electron pair will become positively charged
3.) Some nucleophile substitution reactions from new carbon—carbon bonds (like alkynes)
a. Important because it can extent a molecular carbon skeleton
b. See chart on page 331

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Protic Solvent:

answer

A solvent that is a hydrogen bond donor, in other words there is partially positively charged hydrogen somewhere in the carbon chain. Most common is –OH groups. H¬2O and low molecular weight alcohols or carboxylic acids.

question

Aprotic solvents:

answer

A solvent that cannot serve as a hydrogen bond donor, there are not hydrogen atoms bonded to highly electronegative atoms. Common aprotic solvents are Dichloromethane, Diethyl Ether, Dimethyl sulfoxide

question

Dielectric Constant:

answer

A measure of a solvents ability to insulate opposite charges from one another

question

What are the 2 limiting mechanisms for Nucleophilic substitutions

answer

Sn1 and Sn2

question

Sn2:

answer

A bimolecular Nucleophilic substitution reaction, when the bond breaking and the bonding forming occur simultaneously. 1 STEP!

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Bimolecular reaction:

answer

A reaction in which 2 species are involved in the rate-determining step

question

Describe the Sn2 Reaction mechanism

answer

o Its called bimolecular because both the haloalkane and the nucleophile are involved in the rate-determining step
• Attacks from the BACK SIDE
o Because the polarized C—Br bond the Carbon atom had a δ+ charge and that attracts the electron rich nucleophile.
o Also goes into the antibonding orbital
o The electrodensity of the nucleophile entering from the backside assists in breaking the C—Br bond thus helping the Br leave
• Sn2 Only has one Energy Barrier (ONE STEP) because 5 groups are interacting with the central carbon, its unstable, because the transition compound has a higher internal energy, or standard relative to the reactant/product.  think rubber balls

question

Sn1:

answer

a unimolecular Nucleophilic substitution reaction

question

unimolecular reaction:

answer

A reaction in which only one species is involved in the rate-determining step, the bond breaking between the Carbon and leaving group is completed BEFORE the bond forming with the nucleophile begins.

question

What molecule is involved in the rate-determining step for Sn1 reactions?

answer

ONLY the Halo Alkane

question

solvolysis:

answer

A Nucleophilic substitution in which the solvent is also the nucleophile

question

Some Common Polar Protic Solvents are....

answer

1.) Water (79)
2.) Formic Acid (59)
3.) Methanol (33)
4.) Ethanol (24)
5.) Acetic Acid (6) Moderately polar protic

question

rate is dependent on what?

answer

CONCENTRATION!!!

question

What order is Sn1? Sn2?

answer

sn1= first order
Sn2= first order

question

Sn1 is governed by ___?

answer

Electronic factors (relative instability)

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Sn2 is governed by _____?

answer

Steric Factors

question

Steric Hindrances:

answer

the ability of groups because of their size to hinder the access to a reaction site within a molecule

question

Allylic Carbocations:

answer

a carbocation in which an allylic carbon bears the positive charge. A way for 10 haloalkanes to undergo an Sn1 reaction, they have a double bond next to the electron deficient carbon, more stable then alkyl’s because of the resonance ability.

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allylic:

answer

next to the carbon—carbon double bond

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Benzylic carbocation:

answer

a carbocation in which a carbon attached to a benzene ring bears the positive charge

question

What is the Dielectric constant for Polar, nonpolar and in-between-ers?

answer

polar= 15+
Nonpolar = less than 5
in-between= 5-15

question

Some Common aprotic solvents are... ?

answer

Dichloromethane, Diethyl Ether, Dimethyl sulfoxide

question

Solvents:

answer

dissolve reactants and provide the medium in which a reaction takes place

question

Dielectric constant:

answer

A measure of a solvents ability to insulate opposite charges from one another

question

Protic solvent:

answer

a solvent that is a hydrogen bond donor

question

Aprotic Solvent:

answer

a solvent that cannot serve as a h-bond donor, nowhere in the molecule is there a hydrogen bonded to an atom of low electronegativity.

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Nucleophilicity:

answer

a kinetic property measured by the rate at which a nucleophile causes nucleophilic substitution on a reference compound under a standardized set of experimental conditions

question

Basicity:

answer

An equilibrium property measure by the position of the reaction, for example the acid—base reaction for example the A—B reaction between ammonia and water

question

Strong nucleophile has.... what defining character?

answer

pka higher than 11

question

moderate nucleophile has what defining character

answer

pka of about 11

question

weak nucleophile has what characteristic?

answer

pka lower than 11

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Relative Ions in polar aprotic solvents
(only the halogens)

answer

F- > Cl- > Br- > I-

question

Relative ions in polar PROTIC solvents [only halogens]

answer

I- > Br- > Cl- > F-

question

β-Elimination reaction:

answer

A reaction in which a molecule such as HCl, HBr, HI or HOH is split out or eliminated from adjacent carbons

question

Dehydrohalogenation:

answer

Removal of –H and –X from adjacent carbons, a type of β-Elimination reaction

question

Zaitsev’s Rule:

answer

(or undergo Zaitsev’s elimination) a rule that the major product of a β-Elimination reaction is the most stable alkene. That is with the highest amount of substituents on the carbon carbon double bond

question

E1:

answer

A Unimolecular β-Elimination Reaction or when a bond breaks the carbon-leaving group bond to give a carbocation before a reaction with a base to lose a hydrogen and from the carbon—carbon double bond. 1st order kinetics, product is a more stable alkene substituted with carbon—carbon double bonds.

question

E2:

answer

A Bimolecular β-Elimination reaction where the bond break and make is at the same time. Consider only when hydroxides, alkoxides and acetylides and amides anions are used. 2nd order kinetics has major products

question

Alkynes:

answer

a carbon—carbon triple bond

question

Terminal alkynes:

answer

an alkyne in which the triple bond is between carbons 1 and 2

question

· Describe naming alkynes:

answer

o   “-yn-” is used to show the presence of a triple bond
o   Number the longest chain that contains the triple bond from end to end giving the triple bond priority to the lowest numbers
o   If the molecule has more than one triple bond use “-adiyn-“, “atriyn-“, and so forth

question

Alkylation reaction:

answer

any reaction in which a new carbon—carbon bond to an alkyl group is formed, this is only practical with 1^o and methyl halides, this process is common in lab

question

Dehydrohalogenation:

answer

the removal of the HX from the molecule

question

Allene:

answer

Any compound that contains adjacent carbon—carbon double bonds; that is, any molecule that contains a C=C=C functional group

question

Vinylic Carbocation:

answer

a carbocation in which the positive charge is on one of the carbons of a carbon—carbon double bond

question

Enol:

answer

A compound containing a hydroxyl group bonded to a doubly bonded carbon ato, thinkà alkene (en-) with an alcohol (-ol) resulting in enol

question

Tautomers:

answer

constitutional isomers in equilibrium with each other that differ in the location of a hydrogen atoms and a double bond relative to a heteroatom most commonly O, N or S

question

Keto-Enol Tautomerism:

answer

A type of isomerism involving kept (from ketone) and enol tautomers

question

· what are three ways to make and alkyne into an alkene and alkane

answer

o
Catalytic reduction

o   Hydroboration-protonolysis
o   Dissolving-metal reduction

question

1.) Lindlar catalyst:

answer

Finely powdered palladium metal deposited on solid calcium carbonate that has been specially modified with lead salts. It is particular use is as a catalyst for the reduction of an alkyne to a cis alkene.

question

1.) Syn addition:

answer

the addition of two hydrogen atoms to the carbon—carbon double bond that gives cis alkenes

question

Organic Synthesis:

answer

a series of reaction by which a set of organic starting materials is converted to a more complicated structure

question

Retrosynthesis:

answer

A process of reasoning backwards from a target molecule to a suitable set of starting materials

question

· what is the STRATEGY for solving organic synthesis?:

answer

1.)    Count the carbon atoms of the skeleton of the target molecule. Determine how to build the carbon skeleton from available starting materials is often the most challenging part of a synthesis.
a.       If you must add carbons consider what carbon—carbon bond forming reactions are available to you.
                                                                           i.      Only option that would be given is alkyation of acetylide anions with methyl or primary halides
2.)    Analyze functional groups, how can they change or what needs to be changed.
a.       Keep in mind stereoselectivity and Regiospecificity
3.)    WORK BACKWARDSJ

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