inorganic chem flash - purple (use written notes) Flashcards
what is an isomer
An isomer is a molecule with the same molecular formula but different structural formula
What is a stereoisomers
A stereoisomer is when the order of bonding in each atom is the same but the spatial arrangement of the atom is different in each bond
What are geometric isomers
A geometric isomer occurs when the arrangement of the atom is different in each isomer
Under what circumstances do geometric isomers occur
Occur when there is rotation around a carbon to carbon double bond, also there must be two different groups attached to each of the carbon atoms that make up the bond
What is meant by cis and trans
Cis is groups on the sdame side of the double bond, trans is groups on opposite side of the double bond
How do properties of geometric isomers differ
Geometric isomers can have different physical properties
What are optical isomers
they are non-super imposable mirror images
When do optical isomers occur
When four different groups are arranged vertically around a central carbon atom (chiral carbon)
How do properties of optical isomers occur
Identical but on light
Effect of enantiomers on polarise light
One enantiomer will rotate light in one direction and the other enantiomer in the opposite direction by the same difference. as there is an equal amount of each enantiomer, the rotation would cancel
What is a racemic mixture and why are they described as being optically inactive
A racemic mixture is one that has equal amounts of left and right handed enantiomers, of a chiral molecule
what is nucleophilic substitution reaction
A nucleophilic substitution is when a nucleophile substitutes itself for the halogen atom, this can occur because the positive charge on carbon atom due to polar bonds makes it act like an electrophile
What are the different mechanisms for a nucleophilic substitution reaction
There are two mechanisms for nucleophilic substitution reactions. SN1 and SN2
Talk about SN1 mechanism
The SN1 mechanism is a two step process. Step 1 is the slow rate determining step, the haloalkane undergoes heterolytic fission to form a carbocation intermediate. Step 2 is the first step and it involves nucleophilic attack on the carbocation by a nucleophile.
Talk about SN2 mechanism
The SN2 mechanism involves only one continuous step. The nucleophile attacks the carbon atom from the side opposite the carbon to halogen bond and begins to form a covalent bond with it. At the same time the carbon to halogen Bond begins to break. A transition state is reached, this adapts a trigonal known bipyramidal structure. The reaction is complete by the formation of our fill new bond and the complete break up of the carbon to halogen bond
How can the mechanism for Nucleophilic substitution be determined
In SN1 mechanism, a carbocation Intermediate is formed and this could be a primary, secondary or tertiary Carbocation. Alkyl groups have a positive effect. This means they are electron donating And can push electrons onto the positively charged carbon atom. Therefore it follows that tertiary carbocations are the most stable. This supports that tertiary haloalkanes are most likely to react with a nucleophile In an SN1 mechanism.
What are factors affecting SN1 mechanism
The size of the alkyl groups in the haloalkane Is important, this is known as the something effect. In an SN2 mechanism THE NUCLEOPHILE Attacks the carbon atom from the opposite side of the halogen atom. In tertiary haloalkanes, attack from the side is likely to be hindered because the alkyl groups Will limit access to the carbon atom. Primary haloalkanes I have no more than one alkyl. Group attached to the halogen carbon atom and sort access to the carbon atom will be much easier therefore primary haloalkanes react with nucleophiles in SN2 mechanisms
What are factors affecting SN2 mechanism
The stability of the Carbocation is very important
What are the different types of reactions that involve haloalkanes
The size of the alkyl group is very important (steric effect)
Talk about elimination reactions of haloalkanes
Halo alkanes can undergo elimination Reactions when they are heated under reflux with potassium hydroxide or sodium hydroxide. In the formation of the carbon to carbon double bond the carbon atom, together with a hydrogen atom on an adjacent carbon atom, has been removed or eliminated from the halo alkanes and not replaced, this reaction is known as base induced elimination
Alkenes can be prepared by dehydration of alcohols using aluminium oxide, conc sulfuric acid or conc phosphoric acid. They can also be prepared by base-induced elimination (propan-1-ol to propene)
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Makovniovs rule
is that when a hydrogen halide or water is added to an asymmetric alkene, the hydrogen atom becomes attached to the carbon with the most hydrogen atoms attached to it already. During the reaction of a hydrogen halide or water with alkenes, markovnikov’s rule is used to predict the major and minor products formed.
Alkenes take part in electrophilic addition reactions with:hydrogen to form alkanes in the presence of a catalyst and halogens to form dihaloalkanes.
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haloalkanes can undergo addition reactions with halogen to form haloalkanes
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haloalkanes a hydration reaction with water using an acid catalyst to form alcohols. This is also an addition reaction
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Haloalkanes are substituted alkanes where one or more of the hydrogen atoms is substituted with a halogen atoms
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Mono Haloalkanes contain only one halogen atom. They can be classified as primary,secondary or tertiary according to the number of alkyl groups attached to the carbon atom bonded to the halogen atom
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haloalkanes take part in elimination reactions to form alkenes using a strong base, such as sodium or potassium hydroxide in an ethanol solvent
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Mono Haloalkanes take part in nucleophilic substitution reaction with: aqueous alkalis to form alcohols, and alcoholic alkoxides to form ethers
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Haloalkanes undergo either sn1 or sn2 mechanism reactions
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Alcohols can be prepared from:
Haloalkanes by substitutions
Alkenes by acid-catalysed hydration
Aldehydes and ketones undergo a reduction using lithium aluminium hydride as a reducing agent
Carboxylic acids prepared with acidified permanganate
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Primary amines have nh2 and an r group, secondary have nh and two r groups, tertiary amines have 3r groups.
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Amines react with acids to form salts
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Primary and secondary amines have tertiary bonding, so bp is higher
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Amines are weak bases. The nitrogen atom had a lone pair of electrons which can accept a proton from water.
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Secondary and primary amines become less soluble as chain length increases
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Tertiary amines with low molecular mass are soluble in water
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The stronger the base the higher the pka value
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Benzene is the simplest member of the class of aromatic hydrocarbons
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benzene cant take part in addition reactions
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benzene has Sp2 hybridisation
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in benzene If something has been substituted one of the hydrogens its known as phenyl
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Molecules that have the same molecular formula but different structural formulae are called isomers.
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Stereoisomers are when the order of bondinging in the atoms is the same but the spatial arrangement of the atoms is different in each isomer. There are two types of stereoisomers:geometric and optical.
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when do geometric isomers occur
Occur when there is restricted rotation around a carbon to carbon double bond
facts about geometric isomers
Have two different groups attached to each of the carbon atoms that make up the bond with restricted rotation
Cis or trans
Differences in melting and boiling points
Different chemical properties
optical isomers Occur in compounds in which four different groups are arranged tetrahedrally around a central carbon atom
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facts about optical isomers
Non superimposable images of each other
Can be described as enantiomers
Identical properties
Form racemic mixtures when enantiomers are in equal volume
Enantiomers are basically two super imposable images of each other
state makovnikovs rule
Markovnikov’s rule states that when a hydrogen halide or water is added to an unsymmetrical alkene, the hydrogen atom becomes attached to the carbon with the most hydrogen atoms attached to it already. Markovnikov’s rule can be used to predict major and minor products formed during the reaction of a hydrogen halide or water with alkenes.
