[thorn0123]

1)

Exam question says this:

CH3CH2CH2CH2OH reacts with acid/heat, and i'm suppose to write down what the product is, however i really do not know so i checked the mark scheme and they say the answer is CH3CH2CHCH2 (but-1-ene), however i do not know how they got this. Could anyone let me know what kind of reaction this is, or more specifically what topic it is on the OCR-A exam board?

2)

Petrol contains some branched chain alkanes. The number of carbon atoms per molecule varies between five and nine. Name one branched chain alkane with between five and nine carbon atoms. I put down 1-methylpentane, and the markscheme specifically says do not allow 1-methylpentane, but 2-methylpentane is allowed, could anyone explain this for me? I'm assuming it is because the carbon single bond can rotate and thus 1-methylpentane is not branched, as it can be called hexane, however this is just a guess.

Cheers.

[Emissionspectra]

(Original post by thorn0123)
1)

Exam question says this:

CH3CH2CH2CH2OH reacts with acid/heat, and i'm suppose to write down what the product is, however i really do not know so i checked the mark scheme and they say the answer is CH3CH2CHCH2 (but-1-ene), however i do not know how they got this. Could anyone let me know what kind of reaction this is, or more specifically what topic it is on the OCR-A exam board?

2)

Petrol contains some branched chain alkanes. The number of carbon atoms per molecule varies between five and nine. Name one branched chain alkane with between five and nine carbon atoms. I put down 1-methylpentane, and the markscheme specifically says do not allow 1-methylpentane, but 2-methylpentane is allowed, could anyone explain this for me? I'm assuming it is because the carbon single bond can rotate and thus 1-methylpentane is not branched, as it can be called hexane, however this is just a guess.

Cheers.

1) is a Dehydration reaction, i'm not too sure for number 2.

[EierVonSatan]

1-methylpentane = hexane

i.e. it's not a branch if it's on the end of the chain

[Chris_K_93]

I think for 1) the reaction is an Elimination reaction (Dehydration) where you remove the OH and a H to form H2O and the Alkene.

Edit: On the AS OCR textbook by Heinemann, the reaction is mentioned on page 117.

For 2) 1-Methylpentane is just Hexane and the methyl group is on the end Carbon. It would have to be either 2-Methylpentane, 3-Methylpentane or 4-Methylpentane

[thorn0123]

Thought so, thanks.

[thegodofgod]

(Original post by thorn0123)
1)

Exam question says this:

CH3CH2CH2CH2OH reacts with acid/heat, and i'm suppose to write down what the product is, however i really do not know so i checked the mark scheme and they say the answer is CH3CH2CHCH2 (but-1-ene), however i do not know how they got this. Could anyone let me know what kind of reaction this is, or more specifically what topic it is on the OCR-A exam board?

2)

Petrol contains some branched chain alkanes. The number of carbon atoms per molecule varies between five and nine. Name one branched chain alkane with between five and nine carbon atoms. I put down 1-methylpentane, and the markscheme specifically says do not allow 1-methylpentane, but 2-methylpentane is allowed, could anyone explain this for me? I'm assuming it is because the carbon single bond can rotate and thus 1-methylpentane is not branched, as it can be called hexane, however this is just a guess.

Cheers.

1. You're going from a primary alcohol to an alkene. Therefore, you are losing a molecule of water. The reaction usually uses concentrated sulfuric acid or concentrated phosphoric acid as a catalyst. What type of a reaction is this?

2. 1-methylpentane = hexane. This is because single bonds can rotate. If you had, however, said 2-methylpentane, for example, you would have got the mark.

What you guessed is perfectly correct

[EierVonSatan]

1. It's a dehydration reaction

2. 1-methylhexane is hexane so yes, you can only have 2, 3, and 4 branches on a 5 carbon chain.

[thorn0123]

(Original post by thegodofgod)
1. You're going from a primary alcohol to an alkene. Therefore, you are losing a molecule of water. The reaction usually uses concentrated sulfuric acid or concentrated phosphoric acid as a catalyst. What type of a reaction is this?

2. 1-methylpentane = hexane. This is because single bonds can rotate. If you had, however, said 2-methylpentane, for example, you would have got the mark.

What you guessed is perfectly correct

Do you have any tips on remembering all the catalysts used for each reaction? I always seem to forget, or get them missed up. For example, Ni for hydration with 150 C, H3PO4 for reactions with water, along with high temp and pressure. Then there is conc H3PO4 and heat for dehydration, as well as acidified potassium dichlorate for distil/reflux reactions. Just so much :|

[PrettyLittleLiars]

(Original post by thorn0123)
1)

Exam question says this:

CH3CH2CH2CH2OH reacts with acid/heat, and i'm suppose to write down what the product is, however i really do not know so i checked the mark scheme and they say the answer is CH3CH2CHCH2 (but-1-ene), however i do not know how they got this. Could anyone let me know what kind of reaction this is, or more specifically what topic it is on the OCR-A exam board?

2)

Petrol contains some branched chain alkanes. The number of carbon atoms per molecule varies between five and nine. Name one branched chain alkane with between five and nine carbon atoms. I put down 1-methylpentane, and the markscheme specifically says do not allow 1-methylpentane, but 2-methylpentane is allowed, could anyone explain this for me? I'm assuming it is because the carbon single bond can rotate and thus 1-methylpentane is not branched, as it can be called hexane, however this is just a guess.

Cheers.

question 1: it is a elimination reaction. This is when water is removed from an alcohol to give an alkene. It is in the 2nd module in the OCR A text book in the halogenalkanes section.

Question 2: this is because 1-methylpentane is NOT branched. This equalls hexane because remember how you look for the longest chain? Draw the displayed formula and you will see your mistake.

Hope this helped I am not sure if anyone else told you what I wrote because I couldn't be bothered to read everyone's message