Orgo Unit 4

How do you find the degree of unsaturation?

multiple number of carbons by 2, then add 2, then minus the amount of H’s and divide by 2

What is DU?

degrees of unsaturation, unsaturation is a double bond, this is a reactive site and it is easier to break down (when thinking of fat)

What are the two options for stereochemistry of alkenes?

Z or E, Z is when highest priority groups are on the “zame zide” (like cis), E is when the highest priority groups are on oppisite sides (like trans)

What is markovnikov’s rule?

add hydrogen to the pi bond with more H’s, more carbocation stability for higher priority group

How to form alkenes?

E1 or E2 with dehydration/elimination of alcohols (following Zaitsev’s rule)

What is the mechanism of a simple H-X addition?

the pi bond electrons go to hydrogen because of partial dipole H-X makes, this kicks off the halide, the H will go on the more H’d carbon and the halide goes on less H’d carbon, however with carbocation formation a shift can happen

What is halogenation of an alkene?

when you add Br2 Cl2 to an alkene, there is usually a solvent of CCl4 or CH2Cl that is a non participant

What kind of addition is halogenation of alkenes?

anti, the two halides will add trans

What is the mechnanism of halogenation of alkenes?

there is an intermediate which is a bromium ion, the pi bond electrons go after one of the halides, this makes an epoxide but halide instead of O, then the second bromine will go to the more substituted group, breaking one of the first two groups

What is acid catalyzed hydration of alkenes?

when you add H/OH to an alkene, the solvent is water and an acid (H+/H2SO4)

What happens to stereochemistry in an acid catalyzed hydration of alkenes?

if there is a stereocenter, the reaction is racemic

What is mechanism of acid catalyzed hydration of alkenes?

the pi bond is nucelophile and attracted to H of acid and the H joins, making carbocation, water will join to other carbon (there is partial positive on O now), another water will come in and the lone pairs on O will be attracted to an H of the water that joined and take it, leaving an alcohol group and making H3O, an acid that keeps reacting

How to identify hydroboration-oxidation of alkenes?

a solvent of BH3/THF is added along with OH-, H2O, H2O2

What happens in a hydroboration-oxidation of alkenes?

it is a 2 step reaction, the OH/H are added in syn addition so they are on the same side, anti markovnikov

What is hydrohalogenation of alkenes?

when water and Br2/Cl2 is added to alkene, there will be an an ion formation but anti addition will happen and OH will join, OH and halide will be trans

What happens in Hydrogenation of alkenes?

adding H2 to an alkene, a metal catalyst is added (Ni, Pd, Pt), it will be sun addition and go from an alkene to alkane

How to identify epoxidation of alkenes?

an alkene plus peroxy accident (peroxide is ROOR) so RCO3H/m-cpba will form an epoxide and will be syn addition because it is hard to make a three member ring trans

What happens in acid catalyzed addition of alcohols (to alkenes)?

H and OR is added to an alkene, forming an ether, there is a carbocation formed so possibility of a shift, follows markovnikov

How to identify acid catalyzed addition of alcohols?

an alkene plus H2SO4 or another acid, and an alcohol (ROH)

What is the mechanism for acid catalyzed addition of alcohols to alkenes?

the double bond electrons go after H on acid and take one (following mark) and a plus is formed, then the electrons on O of alcohol go after plus and attach, then another molecule of the alcohol group goes after one of the H’s and takes it

How to identify dihydroxylation of alkenes?

OsO4 is a solvent along with H2O4 and H2O

What happens in dihydroxylation of alkenes?

2 OH groups are added in syn addition

How to identify the two types of oxonolysis?

O3 will be a solvent, (CH3)2S will be the one to only add double bond O and H2O/H2O2 will also add an alcohol

What to do if you see (CH3)2S as a solvent with O3?

it is a simple ozonolysis reaction where the double bond breaks and in it’s place two double bond O’s are formed

What to do if you see H2O2 or H2O as a solvent with O3?

it is the more complicated ozonolysis, the double bond breaks and two double bond O’s are formed in its place but also OH is added in place of an H attached to carbon if there is one present

Basics of naming alkynes

add -yne, if it is terminal you don’t have to add a number, triple bond is less priority than alcohol

How to name alkyne when there is also a double bond?

if one is one an edge, that one gets the 1, other wise the lower number is the -ene then higher number is the -yne

Why is NH2 used as a base instead of OH in alkyne reactions?

OH is turned into water after a reaction which has a lower pka than an alkyne (making reverse reaction more likely), however, NH2 turns to NH3 which has higher pka (worse acid better base) so forward reaction is better

How to spot parent chain extension of terminal alkynes?

when the product has a greater number of carbons (longer parent chain), NaNH2 is usually used with a C-X group like CH3CH2I

How do you make alkynes?

double E2 elimination (taking away 2 Br groups forms 2 extra pi bonds)

What is halogenation of alkynes?

when you add two Br groups or two Cl groups, solvent is also CCl4

What happens when you add 1 equivalent of Br2 to an alkyne (w CCl4)?

they will add anti and there will be a double bond in the product

What happens when you add 2 equivalents of Br2 to an alkyne (w CCl4)?

the product will have no double bonds and each carbon of the original triple bond will have 2 Brs attached

What happens in hydrohalegenation of alkynes?

H-Br is added, it will add markovnikov, 1 equiv will leave product w double bond, 2 equiv will leave product with single bonds

What happens in acid catalyzed addition of water to alkynes?

you use H2SO4 and water and OH/H gets added (only 1 equiv)

What is the issue with the initial product for acid catalyzed addition of water to alkynes?

the product gives OH being on a carbon with a double bond, called enol, which isn’t stable so it undergoes tautomerization

What happens in tautomerization?

the OH turns into a double bond O and the CH2 turns into a CH3, this product is the major product and is called the Keto (ketone)

What happens in hydroboration oxidation of alkynes?

O/OH is added anti mark, uses BH3 or HB(sigmyl)2 or 9BBN plus H2O/OH/H2O2, this will all undergo tautomerization

When can tautomerization occur (what to identify)?

hydroboration oxidation of alkynes (BH3/9BBN/HB(sigmyl)2 along with H2O, H2O2, OH) and acid catalyzed addition of water to alkynes (H2O and H2SO4) with alkynes

What happens in hydration of alkynes?

H/H is added but it can go two ways, if you want end product alkane use H2 and a metal Pt, Pd, Ni, if you want end product cis alkene use H2 and Pd(CaCO3)/Pb(OOCCH3)2 (lindlar’s catalyst) but if you want trans alkene use NH3 and Na0 (sodium metal)

What to do if you see NH3 and Na0 as a solvent with alkyne?

end product will be trans alkene, it is H/H addition

What to do if you see lindlar’s catalyst/Pd(CaCO3) and H2 as a solvent with an alkyne?

you will get a cis end product (alkene) it is H/H being added

What happens in ozonolysis of alkynes?

the triple bond breaks, O3 and H2O are used as solvents, two products are formed a double bond O is formed where triple bond was and C also gains an OH group