organics - amines Flashcards by Jessica Connelly

what is an amine

-derivative of ammonia in which one or more of the hydrogens is replaced by an alkyl group
-have some hydrogen bonding but it isnt as strong as in alcohols - although not in tertiary
-room temp they are liquids

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what are the 3 types of amines

known as aliphatic
-primary
-secondary
-teritary

dependent on how many alkyl groups there are

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what is important about an amine compared to ammonia

the nitrogen has a lone pair of electrons

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what are aromatic amines

-have a N joined directly to the benzene ring

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what are quaternary ammonium salts

-contain quaternary ammonium ions and are related to amines
-but are not amines and do not pocess a lone pair of electrons on the N

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how are amines named

The common way to name amines is to use the alkyl (or aryl) prefix followed by -amine - use this one mainly

The IUPAC systematic name uses the numbered prefix amino- followed by the alkane (or aromatic) stem

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the prep of primary aliphatic amine with NH3 and halogenoalkanes

-halogenoalkanes are reacted with an excess of NH3 dissolved in ethanol at pressure in a sealed conatiner
-by nucleophlic substitution
-NH2 replaces the halogen and NH4halogen is also produced

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what is the general equation for nucleophilic sub with NH3 and halogenoalkane

R-X + 2 NH3 = R-NH2 + NH4X

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why is nucleophilic sub with NH3 and halogenoalkane not as commonly used

-amine product can react further with more of the haloalkane to form secondary,tertiary and quaternary ammonium salts

-problem minimsed by using an excess of conc ammonia

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how does reduction of nitrile compounds work

-formation of a nitrile from a halogenoalkane
-reduction of the nitrile to form an amine

nitrile vapour and hydrogen gas are passed over a nickel catalyst or LiAlH4 in dry ether to form primary amine

the product has one more carbon that the starting material

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general equation for step 1 of reduction of nitrile to form a primary amine

R-X + KCN = R-C triple bond N + KX
with warm ethanol/aqueous alcohol

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what is the general equation for step 2 of reduction of nitrile to form a primary amine

R-C triple bond N + 4[H] = R-CH2-NH2
with LiAlH4 in dry ether
or
R-C triple bond N + 2H2 = R-CH2-NH2
with nickel catalyst and heat

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why is reduction of a nitrile the more common way to produce an amine

-one product rather than a mixture is produced
-the halogenoalkane is impure mixture

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how are primary aromatic amines usually produced

-prepared by synthesis of ntiro compounds using tin and conc HCl
-this process alone would produce the ammonium salt so NaOH is added to give the amine

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what are the steps of the reaction of nitrobenzene to give amine

Step 1- Benzene undergoes nitration with concentrated nitric acid (HNO3) and concentrated sulfuric acid (H2SO4) at 25 to 60 oC to form nitrobenzene

Step 2 - Nitrobenzene is reduced with hot tin (Sn) and concentrated hydrochloric acid (HCl) under reflux to form an acidic mixture that contains the organic product C6H5N+H3

Step 3 - Sodium hydroxide (NaOH) is added to the acidic reaction mixture to form phenylamine

Step 4 - The phenylamine is separated from the reaction mixture by steam distillation

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what is the general equation for the production of an aromatic amine

benzene ring with NO2 on it + 6[H] = benzene ring with NH2 on it + 2H2O
with Sn + HCl followed by NaOH

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are amine B-L acids or B-L bases

B-L bases - proton acceptors

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why are amines weak acids

-are weak acids and act as bases bc they have a lone pair on the N whihc can readily accept a proton

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what effects the strength of an amine

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-ability of the lone pair of electrons on the nitrogen to accept and H/proton and form a dative covalent bond
-the more readily a proton is attracted the stronger the base is or the higher the electron density on the lone pair of the nitrogen

what factors effect the basicity/strength of amines

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-postive inductive effect
-delocalisation

how does positive inducitve effect cause basicity

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some groups such as alkyl groups donate electron density to the nitrogen atom causing the lone pair of electrons to become more avaliable and increasing the basicity

how does delocalisation affect the basicity of the amine attached to a benzene ring

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-presence of aromatic rings such as benzene ring cause the lone pair on the N to be delocalised in the ring
-lone pair becomes less avaliable to form a dative covalent bond with ammonia and decreases the amines basicity

general equation for amine and water to give a primary amine

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R-NH2 + H2O <->R-NH3+ + OH-

general equation to show how secondary amines act as B-L bases

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R1-NH-R2 + H+ = R1-NH2+-R2

what does an amine make when it reacts with an acid and how can it do this

salt base + acid = salt and ion of acid Like ammonium salts, amine salts are soluble ionic compounds, so when the alkyl group is small they are water soluble but become less so as the carbon chain increases

what is the general order of base strength in amines

teritary amine > secondary amine > primary amine > NH3 > aromatic amine

3' , 2' and 1' amine strength compared to ammonia

-the more alkyl groups that are sub on the N in place of H the more electron density is pushed onto the N -this is because the inductive effect of alkyl is greater than that of H - so alkyl groups oush electron density towards the N atom better than H

aromatic amine strength comapred to ammonia

-lone pair on the N is partially delocalised in the benzene ring, leading to a reduction in the electron density on the N atom so weaker base strength

comparison statement bwt strength of amines

-state which is stronger -eg primary amine vs ammonia -then say that the stronger has a greater electron density on the N lone pair -lone pair on N has greater ability to accept H+

what smell do amines have and why

Amines have a fishy smell, which disappears as soon as you add an acid, because you are making an non-volatile salt. Decomposing fish give off amines which are produced by the bacterial decomposition of proteins.

why can the products of nucleophilic substitution react with halogenoalkanes

-the amine also has a lone pair on the N -so this will react with the halogenalkane -the product of the reaction has a higher electron density on the N lone pair and is even better at reacting with halogenoalkanes than the original molecule

what products will you get if you use a large excess of ammonia in nucleophilic substitution

primary amine is the main product

what happens if a large excess of haloalkane is used in nucleophilic sub

quaternary ammonium salt is the main product - all groups surronding the N are alkyl - usually CH3 and whatever orginal group was on

how can nucleophilic sub be affected by electron density

- H on the N can be successively replaced by the R group from the haloalkanes

what is the order of nucleophilic sub reactions to produce subsequent amines

ammonia - primary amine - secondary amine - tertiary amine - salt keep add RX secondary amines are also N sub amines

what are soap and detergent molecules called

-surfactants

what do soaps and detergents consit of

-ionic head /hydrophilic as it can dissolve in water -hydrophobic long alkyl chain tail - this dissovles grease - grease is not soluble in water

how do miscelles form

-when the soap/detergent surround the dirt/grease molecules with the hydrophobic tails in the centre dissolving the grease and the hydrophilic heads on the outside dissolving in the water

what are used as cationic surfactants

-quaternary ammonium salts with long alkyl chain -fabric softners often contain these as most of the surface material is -ve charged

nucleophilic addition elimination of amines

-amines can react with acid anhydride or acyl chloride to replace the H on the N with the acyl group -produces an amide and a molecule of HCl or carboxylic acid depending wether an acyl chloride or acid anhydride is used -a second molecule of amine reacts with HCl/ carboxylic acid to form a salt

second equation for producing an salt - nucleophilic addition - elimination

H+ + RNH2 = RNH3+

Explain why an aqueous solution is obtained in this reduction even though phenylamine is insoluble in water.

C6H5NH2 present as ionic salt OR C6H5NH3 + (Cl–) OR phenyl ammonium (chloride)

conditions of nucleophilic substituition with ammonia

-excess ammonia -ethanolic -hot, under pressure

conditions for the second stage of reduction with nitrile

- Nickel catalyst and H2 -LiAlH4 in dry ether

uses of quaternary ammonium salt

-cationic surfactant -detergant/fabric softener -hair conditioner

remember to add on halogenoalkane ion at the end of the equation - nucleophilic sub of ammonia/amine

why is it bad to use acyl chlorides/acid chloride and what is a better reactant to use

-produce hydrogen chloride -more expensive -more reactive -use acid anhydride -more controllable reaction

organics - amines Flashcards

(47 cards)