Aldehydes and ketones 2 Flashcards
How do you protonate a H on the alpha C
With a really strong alkaline catalyst. Leaves a negatively charged alpha C (shared with O in ressonance form)
Enolate Def
Salt of an alcohol with a negative charge on the O. Part of resonance form after H leaves aldehyde/ketone. Acts as a nucleophile in aldol formation
Requirements for aldol formation reaction
A strong alkaline catalyst and at least 1 H on the alpha C
Enal Formation Outline
Adol is dehydrated at a high temp (loses H2O. H = original nucleophile, OH = from original electrophile). Also known as carbonyl condensation reaction
Colllagen Structure outline
Made up of 3 tropocollagen monomers. Each tropocollagen monomer is made up of 3 helices held together by H bonds, inter and intra molecular cross links (covalent bonds). Amount of cross linking indicates strength of collagen
What is the dehydration step controlled by in aldol condensations
Enzyme: lysyl oxidase. Lysines (amino acid side chains) oxidised to include ketones/aldehydes
What removes water in dehydration part of aldol condensations
Enzyme. This enables an enal cross link to be formed. This is due to the fact tat heat would denature the protein
Oxidation Level of a C outline
The number of bonds between C being evaluated and substituents that are not another C or H (1st atom attached is counted). The higher the oxidation level = the more oxidation that has occurred. (NB oxidation level isn’t oxidation state)
Product of aldehyde reduction
primary alcohol (since 1 substituent is H it means that C can only be attached to one other C)
Product of ketone reduction
Secondary alcohol
Lab reducing agents
Hydride Ion. Negatively charged H due to the presence of 2 electrons
Biological reducing agents
NAD+ and NADP+
Which are more easily oxidised Aldehydes or ketones
Aldehydes (when doing oxidation tests. Positive = aldehyde)
Tollen’s Reagent Test Outline
Aldehyde is oxidised percipitating Ag. Forming a silver mirror colour in test tube
Fehling’s solution outline
In presence of aldehyde copper is reduced (and percipitated). Solution goes from royal blue to brick red colour
Steps in secondary alcohol oxidation
secondary alcohol to ketone
Steps in primary alcohol oxidation
primary alcohol to aldehyde to carboxylic acid
Only time primary alcohol oxidation stops at aldehyde
When pyridinium chlorochromate is used as oxidising agent
