Organic Chemistry - Top TIPS! Flashcards by Hana bashir

If there are, for example, TWO methyl groups on the THIRD CARBON then remember ….

the name should include 3,3-dimethyl***

NOT JUST ONE 3.

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Explain when brackets are used in structural formula using CH(CH3) as an example

This means the CH3 in brackets is coming off of the same C as the one written just before in CH.

So basically you draw the thing in the brackets coming directly off of the carbon written before

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What do brackets in structural formula show?

that the polyatomic group inside the bracket, when drawn in displayed formula, should be attached to the nearest non-hydrogen atom on the left

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What should you write in the brackets in structural formula if you have

an ethyl group [CH2CH3] coming off of a carbon?

Two methyl groups coming off of the SAME carbon?

(C2H5)
Eg. CH(C2H5)

C(CH3)2

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How would you draw an ethyl group coming off of a carbon in skeletal formula?

Sideways open triangle coming off of carbon

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When drawing displayed formulas what should you always check for

that everything has 4 bonds!

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butylcyclohexane

cyclohexane with C4H9 attached - really similar to butane but one less hydrogen because it isn’t BUTANEcyclohexane, it is just BUTYLcyclohexane

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Formula for number of isomers up to and including heptane? (works for alkanes NOT ALKENES)

2^n - 4 +1 (where n= no. carbons)

eg. isomers of heptane = 2 to the power of 7 -4 gives 2 to the power of 3 which is 8, then +1 gives 9. So heptane has NINE ISOMERS.

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how do you read the groups on the carbon chain so you can write the name?

always read them so that in the name (so like 2,2,3 di-methylbutane or something) the numbers are the smallest they can be.

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How to logically draw isomers

Draw the main chain

Chop off a carbon and add a methyl group to as many places as possible to get different isomers

Chop of a second carbon and work out isomers with two methyl groups

chop off a third carbon and see if there is an isomer with three methyl groups

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when counting a carbon chain… (about what is on the carbon)

even if one of the carbons has no hydrogens attached to it, it is STILL part of the carbon chain

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when drawing chlorines onto skeletal formula…

don’t draw it directly at the end of the line representing the carbon, draw another mini line at another angle and then put Cl

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Give an example of a diol

pentan-2,3-diol

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If you are drawing a diol from an alkene then the …

two OHs should attach to the carbons either side of the carbon=carbon double bond

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If there is a 4 carbon chain and a methyl group AND a bromine attached to the 2nd carbon then it is called…

2-bromo-2-methylbutane (so the bromo first then the methyl groups)

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which mechanism involves markovnikov? And what is the rule?

alkene + hydrogen halide

Add the hydrogen to the carbon in the C=C that already has the most hydrogens, then the + goes on the other carbon

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If a question asks you to show three repeating units of the addition polymer formed from X…

three repeating units so DON’T use brackets (these are only for showing one repeating unit when you include a C=C double bond).
Use single bonds

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X is made from the addition polymer (w/o brackets) shown below. Give the formula of X….

so it would be in brackets and a double C=C of the addition polymer - this would represent it as a repeating unit because lots of those units make X

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How would you write the structural formula for a carbon with a methyl group AND another group (eg. bromine) on it?

CBr(CH3) - soalways write the methyl group after the other group

NOT C(CH3)Br

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How do you write the structural formula for cyclo coumpounds?

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cyclo - (eg.)CH3CH2CH3CH2 -

Outline how to prepare 2-brompentane in a lab?

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heat Pentan-2-ol under reflux with 50% concentrated sulphuric acid and potassium bromide.

In the alcohol plus halogenating agent reactions (which either produce, bromo,iodo or chloro alkanes), if you want to produce an alkane where the halogen is on a particular carbon (eg. 2-chlorobutane) then….

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you use an alcohol where the OH is on the carbon you want the halogen to be on. So… butan-2-ol

Two equations for ALCOHOL + IODINE + RED PHOSPHORUS reactions

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1) P + 1.5I2 –> PI3

2) PI3 + 3C3H7OH –> 3C3H7I + H3PO3

Two equations for ALCOHOL + POTASSIUM BROMIDE + 50% CONC SULFURIC ACID reactions

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1) first the sulphuric acid + potassium bromide: H2SO4 + KBr –> HBr + KHSO4
2) Then the hydrogen bromide that has formed reacts with the alcohol: HBr + C5H11OH –> C5H11Br + H20

halogenoalkane + KOH equation and ionic equation

halogenoalkane + KOH --> alcohol + K *halogen* eg. C3H7Br + KOH --> C3H7OH + KBr Ionic: halogenoalkane + OH- ---> alcohol + *halogen* (basically remove the K)

which mechanism has three curly arrows all on one compound and where are they?

elimination reaction of halogenoalkanes + ethanolic KOH --> alkenes OH- ion acts as a BASE arrow towards H on end Carbon arrow from that C-H bond to the nearest C-C bond arrow from the C-halogen bond to the halogen

ammonia mechanism

halogenoalkane + ammonia --> primary amine slow: Dipole on carbon and halogen so NH3 attracts to delta + carbon and there is a curl arrow showing the halogen breaking off. Forms previous hydrocarbon with NH3 attached + the halogen that broke off fast: another NH3 comes in and takes a H from the already attached NH3 (first curly arrow), then one curly arrow from that H-N bond to the N. Forms a primary amine and ammonium

Which classifications of halogenoalkane react via Sn1 and Sn2?

Sn1 - secondary/tertiary | Sn2 - primary/secondary

If it says X reacts by Sn2, give the Sn1 mechanism it means that...

X must be secondary and can therefore either react by Sn1 or Sn2

How to classify stuff?

look at the number of CARBONS attached to the carbon with the functional group attached to it

when drawing a transition state where should the >group that is like C3H5 go >CH3 group go >H go

>single vertical line up from central carbon >wedge at bottom > dashed line at bottom

If the question asks you to draw the Sn1 AND Sn2 mechanisms for a secondary halogenoalkane how do you draw them?

SN1: with displayed formula SN2: with wedges, dashed lines and solid lines. The negative species should be horizontal to the central carbon (solid line)

How to write C=O in structural formula?

just do CO

How to write COOH (carboxylic acid) in structural formula?

CO2H

ALWAYS REMEMBER TO MAKE SURE EVERYTHING HAS

4 BRIAN THE OLD FUCKER BONDS ONLY

What is the elimination equation in the section about alcohols and oxidation?

alcohols reacting with phosphoric acid --> alkene + water | but DO NOT include H3PO3 in the equation *find out why*

How do you know when to draw intermediates of mechanisms in displayed formula or with wedges and dashed lines?

If the intermediate is a carbocation then draw it as displayed If the intermediate isn't a carbocation then draw it with dashed lines and wedges

what do polymerisation reactions require?

an initiator

if a halogenoalkane has 2+ halogens (eg. one chlorine and one fluorine) how do you decide which bond breaks in the mechanism (eg. if a bond needs to break because an OH- is substituting in)

the weakest bond breaks. (Fluorine is very strong so CHLORINE bond would break)

What enables nucleophilic substitution reactions to take place?

the lone pair of electrons on the nucleophile

reforming equation example C7H16 -->

C7H14 +H2

general equation for | Alkane + halogen -->

alkane + halogen --> halogenoalkane + hydrogen halide

What is another name for reforming?

dehydrogenation

How do you know if something can be named with Cis/Trans or E/Z?

Look at the C=C bond, if the 4 groups are all completely different to each other then it is E/Z. But if each group on the carbon is different to its counterpart (eg. one C has a Cl and a H whilst another C has a Br and a H - so there are still H's in common, then it is CIS/TRANS)

If something is reacting with bromine water what will it have added to it?

an OH and a Br

conditions for initiation in free radical substitution

UV light (photochemical reaction - reaction brought about by light)

4 reasons why cracking of large alkanes is important in industry?

1) makes petrol 2) smaller chains alkane in higher demand + more useful + burn more efficiently 3) makes H2 4) recycles waste products

free radical substitution safety precautions (3)

UV goggles fume cupboard gloves

when drawing isomers, if you are stuck what should you do?

draw the carbon chain and stick the main atom (eg. a Br) onto the end/someone where you heart says to put a hydrogen and it would be really weird to put anything else (put it where it feels uncomfortable!!)

Organic Chemistry - Top TIPS! Flashcards

(49 cards)