Chapter 18 Flashcards
Aldehydes and ketones contain substituents that cannot stabilize a _______ charge (ex C and H):
1) these are _______ leaving groups
2) no acyl _______ reactions
negative
1) poor
2) substitution
the C=O bond is _______, _______, and _______ compared to the C=C bond
shorter
stronger
polarized
What is the IUPAC ending for aldehydes
-al
What is the IUPAC ending for ketones
-one
Common aldehydes and ketones (for C=O compounds: 1C = _______; 2C = _______)
Form
Acet
IUPAC Ketones:
1) number the chain so that the C=O has the _______ number
2) Replace the alkane -e with _______
3) In cyclic ketones, the carbon is assigned number ____
4) if deciding between the C=O and C=C, _______ wins
1) lowest
2) -one
3) 1
4) carbonyl
IUPAC Aldehydes:
1) the aldehyde carbon is always number ____
2) replace the alkane -e with _______
3) if CHO is attached to a ring, the suffix _______ is used
1) 1
2) -al
3) carbaldehyde (carboxaldehyde)
- in this case there are “2 roots”
carbonyl as a substituent: on a molecule with a higher priority functional group, a ketone is an _______ and an aldehyde is a _______
oxo
formyl
Boiling points:
1) Ketones and aldehydes are more _______, so they have a _______ boiling point than comparable alkanes or ethers
2) they cannot hydrogen bond to each other, so their boiling point is _______ than comparable alcohols
1) polar; higher
2) lower
Alkanes<ethers<aldehydes<ketones<alcohols
solubility of ketones and aldehydes:
- they are good solvents for _______. Lone pairs of the electrons on the oxygen of the C=O can accept a hydrogen bond from OH or NH. miscible in water
alcohols
What reagents are needed to turn carboxylic acid into a ketone?
1) 2 eq RLi, ether
2) H3O+
- 1 eq of grignard deprotonates
What reagents are needed to turn nitriles into ketones?
1) Grignard (PhMgBr), ether
2) H3O+
- PADPAD
What reagents are needed to turn nitriles into aldehydes?
1) DIBAL-H
or (i-Bu)2Al-H
2) H3O+
What reagents are needed to turn Carboxylic acids into acid chlorides and aldehydes?
1) SOCl2
2) LiAlH(OtBu)3
What reagents are needed to turn Carboxylic acids into acid chlorides and ketones?
1) SOCl2
2) R2CuLi (Gilman)
What reagents are needed to turn esters into aldehydes?
1) DIBAL-H
2) H2O
What are the steps to nucleophilic addition (basic)
1) attack
2) protonate
- no strong acid allowed and good Nuc- needed
What are the steps to nucleophilic addition (acidic)
1) protonate
2) attack
3) deprotonate
- needs strong acid and weak Nuc: used
What are the 2 factors that effect the reaction rates of aldehydes and ketones in nucleophilic addition?
1) steric
2) electronic (inductive)
- δ+ needs to be attacked so open and unstable = more reactive [small groups and EWG :) ]
rates of aldehydes and ketones in nucleophilic addition:
The larger the R-groups on the C=O, the _______ the reaction
slower
rates of aldehydes and ketones in nucleophilic addition:
- EWG = _______
- EDG = _______
EWG = destablized δ+ = more reactive
EDG = stablized δ+ = less reactive
aldehydes and ketones react with water to give _______ diols
geminal
The addition of water to aldehydes and ketones is an equilibrium reaction that is _______, and nucleophile attack of H2O can be catalyzed by basic and acidic conditions
reversible
- favoring carbonyl (reactant) compounds
Aldehydes and unhindered ketones react with HCN to give _______
cyanohydrin
Aldehydes and unhindered ketones react with HCN to give cyanohydrin, which works best under slightly _______ conditions
basic
- will favor tetrahedral product in most cases unless extended conjugation (phenyl)
Addition of HCN to acetophenone is less reactive than acetone because:
1) product has higher energy compared to starting acetophenone because it is less _______
2) the benzene ring introduces _______
1) conjugated
2) sterics
- both because of the benzene ring
adding an EDG to phenyl on acetophenone will result in a _______ reaction
slower
- stabilizes carbonyl (making it less electrophilic) (less attackable)
Formation of imine (C=N-R) occurs under slightly _______ conditions
acidic
- PAD PAD
What is another name for imines?
Schiff base
- have to contain an R group though
What is the name for the most stable intermediate in the mechanism for formation of imines?
carbinol amine
aka hemiaminal
What’s the difference in mechanism for the formation of imines if there is a 2° amine instead of a 1° amine? What is the name of the molecule it forms?
at the end of 2° amine addition, the 2nd hydrogen is taken 1 away from the carbon attached to the Nitrogen
- forms enamine (nitrogen on a double bond)
Imine products should always be drawn _____
(E)
imines are nitrogen analogues of ketones and aldehydes with a _____ bond in place of the carbonyl group
C=N
make sure to learn names of other condensations with amines
https://quizlet.com/1021257036/other-condensations-with-amines-diagram/?i=1ha23w&x=1jqt
Synthesis of acetals is _______ and equilibrium often favors the _______
reversible
reactants
- remove water (lechatelier’s) to drive rxn forward
What are the steps (ex PAD) for formation of acetals?
PADPAAD
What is the nucleophile for hydrolysis of acetals?
H2O
Reagents: H3O+
useful in synthesis
Formation of acetals requires slightly _______ conditions
acidic
hemiacetals are not favored at equilibrium even though they are super stable. The only exception found in nature is a _______ hemiacetal
cyclic hemiacetal
Often a _______ is used in the preparation of acetals. the reaction is more favorable because the conversion of a hemiacetal ——> acetal is reversible
diol
- intramolecular tethered system, so it is faster than any competing nucleophile
aldehydes form acetals _______ than ketones, allowing for selective protection of different carbonyl functional groups
more
The Wittig reaction converts a _______ into a new _______
C=O
C=C
- this is why it won a nobel in 1979
The Wittig reaction requires a _______ that is used as the nucleophile in the reaction
phosphorus ylide
Phosphorus ylide is prepared from triphenylphosphine and an unhindered alkyl halide = _______, butyl lithium is then used to abstract a hydrogen from the carbon attached to the phosphorus to form the ylide
Sn2
In general, the ylide should come from an _______ alkyl halide (ensures fast reaction)
unhindered
- cuz Sn2
Wittig reaction products should always be drawn _____
(Z)
- cis
_______ test involves adding a solution of silver-ammonia complex to the unknown compound to test for _______
Tollen’s
aldehydes
What is the best reagent to use for oxidation of aldehydes?
Ag2O
- oxidizes only aldehyde not DB
What are the two ways to deoxygenate a ketone or aldehyde?
1) Clemmensen reduction
2) Wolff-Kishner reduction
- takes of C=O
What are the reagents for Clemmensen reduction?
Zn(Hg), HCl, H2O
What are the reagents for Wolff-Kishner reduction?
1) NH2NH2 (hydrazine), pH~4.5
2) KOH, Δ
- step 2 is true WF red, wf red works on imines and oximes formed by step 1
In what scenarios would Clemmensen be used over Wolff-Kishner reduction?
1) When you start with a Carboxylic acid
2) Get rid of acetal
3) Turn nitro into amine
In what scenarios would Wolff-Kishner reduction be used over Clemmensen?
1) When you have amides in OG compound
2) keep acetal
3) keep nitro
