Problem when compiling

i am trying to compile chapters of my thesis with texmaker. When i play F6 the console log file returns:

The log file is very large, i paste part of it:

This is pdfTeX, Version 3.14159265-2.6-1.40.15 (TeX Live 2015/dev/Debian) (preloaded format=pdflatex 2017.5.25)  26 MAY 2017 00:46
entering extended mode
restricted \write18 enabled.
%&-line parsing enabled.
**intro.tex
(./intro.tex
LaTeX2e <2014/05/01>
Babel <3.9l> and hyphenation patterns for 5 languages loaded.

! LaTeX Error: Missing \begin{document}.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
...

l.1 L
as computadoras han permitido la expansiÃ³n de diversos campos cientÃ­f...

You're in trouble here.  Try typing  <return>  to proceed.
If that doesn't work, type  X <return>  to quit.

Missing character: There is no L in font nullfont!
Missing character: There is no a in font nullfont!


Thank you for helping. Any advice will be welcome

• It will list where the error is (line number). Please post the full log file. Also, don't use \large in \chapter  that's a very bad idea. – daleif May 26 '17 at 4:43
• I didn't face any error when compile your code, if possible, please post your .log file – MadyYuvi May 26 '17 at 4:48
• @MadyYuvi i edited. Some other chaptes do not produce .log. I do not know why. But it would be a less important problem – santimirandarp May 26 '17 at 4:54
• Go to your main buffer and click on Make this the master file somewhere in the Texmaker interface. You can hit compile from your chapter files now as well. – Johannes_B May 26 '17 at 8:55
• Declaring the main file as master makes texmaker remember that it has to compile the master file, even if one of your chapter buffers is open. There really is no magic behind it, but reading an introduction to how LaTeX works might help you understand it better. – Johannes_B May 26 '17 at 9:09

The wrong file intro.tex is compiled. It starts with the text Las computadoras. Look for the file that starts with \documentclass and compile this file with LaTeX.